Originally Posted by naanbread
what do u mean by unplugging the varible intake manifold?
The 1.8 and 2.0 TS motors have a special intake manifold that winds a set of longer intake tracks on at low RPM for more power.
If you unplug it you will always have short intake tracts, and more noise, but compromised low down power.
My personal recommendation would be to not do that, then leave the intake as standard, but use a higher flow paper filter.
Maybe take the resonator inside the bumper off if you want more noise. But be aware that it was put there to do more than make it quieter, expect a less uniform power curve.
The problems with the K&N above:
-Heat, it only works at higher speeds, away from the lights you're sucking hot air from the engine bay and have less power.
-Moisture, anything but a paper filter lets significant levels of water vapour past, water vapour prevents the hot wire MAF from metering the air correctly and also damages the MAF, shortening its lifespan.
You also want to remember that these cars have a well designed intake, there's not much better you can do, and if you can, you're probably looking at less than 1bhp improvement. Use a K&N on something like a Corsa by all means, there is plenty of room for improvement there.