Originally Posted by andrey_gta
As exhausts go, the power gains are from deleting catalytic converters. The gains are in the low to mid end of RPM.
Sound is mostly form the muffler/axel back of your choice, some even go without mufflers.
Deleting the resonator will add that burble/grumble at shift points.
The European airbox can be cut at the indent for the headlight access to gain more sound, colder air and perhaps some power. Its will resemble the current AFE magnum intake for our cars. the 130i guys have tested this with dyno's.
So get a 2" or 3" circular rubber plug form a home hardware type store, drill with the appropriate hole maker attachment and experiment. Plug it up if you dont like.
The euro box also accepts euro K&N drop in filter which is the oiled version of the one the euro BMW Performance airbox uses. AFE offers both oil and dry versions. Both available online( amazon, ebay and other) for substantial discounts over official K&N and AFE websites.
Thanks for your quick response Andrey, The drop-in filter sounds the most appealing option simply because it's a replacement rather than modifying what's already there, but will that make a noticeable difference in sound?
I'd be inclined to try cutting a hole in the airbox and then maybe feeding a hose to it from behind the grille if possible, as you say it is reversible by plugging it up but not ideally what i'd like to do. I get the impression this will give a bit more of a modified sound than i'm after from past experience aswell, not to mention filling my airbox with crap? Maybe i'm wrong it's just a thought..?
Thanks again, J