If you're looking to squeeze a bit more juice out of your VQ35DE, starting with a 350z manifold intake upgrade is usually the smartest move you can make. It's one of those modifications that actually feels like it does something the first time you pull out of the driveway. Unlike some "performance" parts that just make the car louder without adding any actual speed, messing with the intake plenum on a Z addresses a genuine design flaw from the factory.
The V8-sized ego of the 350z is sometimes held back by its V6-sized lungs. If you look at the stock plenum on the original DE engine, you'll notice it slopes down toward the front. This was mostly done to clear the hood line, but it creates a massive bottleneck for the front two cylinders. They just don't get as much air as the others. By swapping out or modifying the manifold, you're basically letting the engine breathe the way it was supposed to from the beginning.
Why the Stock Setup is Holding You Back
The VQ35DE engine is a workhorse, but Nissan definitely prioritized the sleek hood profile over optimal airflow for the early 350z models. The "sandwich" design of the intake manifold means the air has to navigate some pretty tight spaces before it ever reaches the combustion chamber. When you're at high RPMs, that cramped space becomes a real problem.
The front cylinders are essentially starved of air compared to the rear ones. This doesn't just hurt your horsepower numbers; it can actually lead to uneven engine wear over time because the cylinders aren't running under the same conditions. When people talk about getting a 350z manifold intake upgrade, they're usually trying to level the playing field for all six cylinders.
The Famous Plenum Spacer
If you're on a budget—and let's be honest, most of us are—the plenum spacer is the go-to mod. It's exactly what it sounds like: a piece of machined aluminum or thermal polymer that sits between the upper and lower halves of the intake manifold.
By adding that 5/16" or 1/2" of space, you're lifting the "lid" of the engine's lungs. This allows much more air to reach those front cylinders that were previously gasping. * 5/16" Spacers: These are the most popular because they usually fit under the stock strut bar without any drama. You get a nice bump in mid-range torque and a few extra ponies at the top end. * 1/2" Spacers: These offer even more volume, but you'll almost certainly have to mess with your strut bar or buy a spacer for the bar itself.
It's probably the best "bang for your buck" modification in the Z world. You can install it in an afternoon with basic hand tools, and you'll actually feel the difference in the mid-range.
Stepping Up to the MREV2 Lower Manifold
If you've got a "RevUp" version of the 350z (the 300hp version found in 2005-2006 manuals), the plenum spacer helps, but it doesn't solve everything. The RevUp engines actually have a worse lower manifold design for mid-range torque than the original non-RevUp engines.
This is where things like the Motordyne MREV2 come into play. This is a modified factory lower 350z manifold intake that has been CNC machined to improve flow. When you pair an MREV2 with a plenum spacer on a RevUp engine, the gains are actually pretty ridiculous for a naturally aspirated mod. You're looking at a massive gain in area under the curve, making the car feel much punchier when you're just driving around town, not just when you're redlining it.
Full Manifold Replacements
Some people decide to ditch the factory "pancake" style plenum altogether. You've probably seen the shiny, polished manifolds from companies like Kinetix or the heavy-duty cast versions that look like they belong on a race car.
Kinetix Velocity Manifold
The Kinetix manifolds are iconic in the 350z community. They replace the entire upper plenum with a high-volume tank. They look great when you pop the hood, and they definitely flow better at high RPMs. However, some owners have noted that you might lose a tiny bit of low-end torque compared to a spacer setup. If you're building a dedicated track car or a high-revving street beast, it's a solid choice.
The "Long Runner" Style
Then you have the really serious setups that look like a spider sitting on top of the engine. These often require significant modifications, including moving the throttle body or changing how your intake piping is routed. They're great for forced induction builds, but for a daily driver, they might be overkill.
Dealing with Heat Soak
One thing people often forget when messing with their 350z manifold intake is heat. The VQ engine bay gets incredibly hot. Since the manifold is made of metal and sits right on top of the engine, it acts like a giant heat sink. When that manifold gets hot, the air inside it gets hot, and hot air is less dense—which means less power.
While you're in there doing a spacer or a manifold swap, it's worth looking into thermal gaskets or "ISO-thermal" kits. These include aramid gaskets that prevent the heat from the lower engine block from soaking into the upper plenum. It keeps the intake charge cooler, which helps maintain consistent power even after you've been doing some spirited driving for twenty minutes.
The Installation Process: What to Expect
The nice thing about working on the 350z manifold intake is that it's all right there on top. You don't have to crawl under the car or drop the subframe. That said, it's a bit of a "bolt-fest." There are about 18 bolts holding that plenum down, and they have to be tightened in a very specific sequence and to a very specific (and surprisingly low) torque spec.
- Don't over-tighten: The plenum is made of relatively soft aluminum. If you go at it like a gorilla, you will strip the threads in the lower manifold, and then you're in for a very bad day.
- Watch the gaskets: Make sure your gaskets stay seated. A vacuum leak after an intake install is a nightmare to track down and will make your idle jump around like crazy.
- The "Oil in the Intake" surprise: Don't be shocked if you open up your manifold and see a thin film of oil. That's just the VQ's PCV system doing its thing. It's a good time to install a catch can while you've got everything apart.
Is a Tune Necessary?
You'll hear a lot of debate about this. Can you run a 350z manifold intake upgrade without a tune? Yeah, the car's ECU is smart enough to adjust a little bit. It won't blow up. But if you want to actually see the gains you just paid for, you really need a tune (like UPREV or EcuTek).
Adding more air to the engine without telling the computer to add more fuel usually results in the car running a bit lean. A professional tuner can map out the new airflow characteristics and make sure your air-fuel ratios are spot on. Plus, they can bump up your timing to take full advantage of the improved breathing.
Final Thoughts
At the end of the day, the 350z is a fantastic platform, but it's an older one. The factory intake design was a compromise. Upgrading your 350z manifold intake is essentially "fixing" the car rather than just modding it. Whether you go with a simple 5/16" spacer or a full-blown aftermarket plenum, you're giving the engine the air it's been craving since it left the factory.
It makes the throttle feel more responsive, the exhaust note changes just a tiny bit (usually a deeper growl), and the car pulls much harder through the mid-range. Just take your time with the installation, don't strip the bolts, and definitely consider a tune afterward to tie it all together. Your Z will thank you for it every time you hit the gas.