Start with a free-flowing intake system, or at least make your own using a drop-in K&N filter and a hole saw to perforate your airbox to create better airflow. But then there's the Mass Air Sensor itself, which can be modified -- on SOME cars -- to gain power. Please read this ENTIRE text before you go destroying anything on your car.
If you have a 95 or newer car, stop reading here. For the 95+ cars, there's not much you can do. The airflow sensor is quite large (it's the same part as on the 320 hp 3000GT VR4), and it is not a significant restriction in the intake. More importantly, the 95-99 car DOES NOT RUN WELL if you remove ANY of the honeycombs on the MAS.
On first-generation cars (89-94), there are a couple of ways you can gain a little power.
First, you can remove the little "silencer" unit that sits behind the sensor. It's a folded piece of cardboard in a metal frame. The whole assembly is designed to reduce intake noise. Since you don't care about that, throw it out, and enjoy (slightly) better airflow. Click the picture for a closer look at the silencer.
Second, you can promote a slightly leaner air/fuel mixture by removing the honeycombs from the BYPASS section of the sensor. This is the smaller, oval-shaped section of tubing. Remove the little rivets, and pull out the small honeycomb piece. (This is NOT reversable, so make sure you really want to do this.) Removing this honeycomb will allow more air to flow through the bypass side, reducing the amount of air the ECU THINKS is getting into the motor. This will cause your full-throttle fuel mixture to be slightly leaner, and since the car runs quite rich from the factory, you will gain a little power. Just to reiterate, this DOES NOT APPLY to the 95-99 cars. If you remove the honeycombs on the 95-99 turbo MAS, it will run and idle very badly, and you'll see no increase in power.
Finally, there is a screw that pokes into the bypass passage. You can back that screw out of the passage to let still more air through the bypass side. If you're doing this, you probably want to have an air/fuel meter to monitor your full-throttle mixture. Generally, this is a perfectly safe mod, but you should always be careful when messing with your air/fuel mixture.
DISCLAIMER: The MAS is a sensitive piece of electronic equipment, and it is EXPENSIVE to replace. Do these modifications at your own risk. We cannot guarantee your car will idle well after performing these modifications. In fact, we can't guarantee anything regarding these mods. Do them AT YOUR OWN RISK.
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