my mk2 uses a airbox with the insides gutted and the trumpet removed and a K&N panel filter, on the dyno we removed the box and left the inlet open, and acheived absolutley nothing when it ran again! good enough for me. ebay chips are very hit miss as above. i would gut airbox and get a decent panel filter, get a cam, then if you want to consider manifolds or ported heads, however i would go mad spending loads of money, unless your an 8v nut!
Be wary of fitting high lift cams. You can only go to approx 256/260 degree cams before the management system throws a wobbly. So assuming the came are 256/260s, look at the lift - if there is a bit gain in lift, you may be ok, but if you are keeping the lambda sensor and Cat, and want it to be legal, it's a minefield when fitting came to an ABF. Assuming you do get cams to run, all you will do is move the torque up the rev range...you will get more power, but lose low end torque. Some of the aftermarket cams are designed for KR or ABF and in reality, aren't much more aggressive than standard ABF cams...so an utter waste of money. Get a ported head, and see if you can have TSR deck the block to raise the compression a bit...maybe just 0.5 to 1.0 on the CR. That, along with a adjustable cam pulley (to get the cams timed back in properly) and standard cams will give you a torque increase everywhere, a slight power gain top end, but not suffer the low end drop off My advice would be standard cams, ported head and a decent re-map and leave it at that, unless you can get the CR up a bit. If you are happy having that done, all well and good...that'll help torque. What I would do instead of cams, is change the gearbox final drive from the standard 3.67 to a 3.94. That will gear the car down, and (along with the lightened flywheel) make it feel like you've added 20+ BHP
Is the car a daily driver, and do you do many long trips in it? If not, look for a lower ratio gearbox maybe, fit slightly lower profile tyres, and look at air box/exhaust/mild cam mods. All the stuff about cams, X-Flow heads, remaps, head porting and block decking, manifolds, air filters... it can all help, but in the end you could spend well over a grand on it, and it'll STILL be slower than a standard Mk3 with 16v ABF, or a Mk2 with 16v KR engine. Unless you're very attached to the car, you might be better to try and find a quicker base model, and then play with that. If you can't afford to upgrade, then airbox and filter mods, cam, and maybe an ebay chip, but don't expect it to breathe fire!
End of the day its not really worth trying to tune an 8v. Spend your money on a 16v or Vr if you want more power.
