troubles with my mk3

okay, first question, what does a shimmed wastegate do? second, i recently bought a weapon-r intake and i could tell it added some kick to the car. especially when the turbo kicks in and off starts. the thing is, ever since i installed it it has caused problems. started with a skip, now that seemed to have gona away and now it idles really low and the car seems bogged down. the mechanic says its either the intake or the ECU. i unhooked battery, dissconected ECU as well as the EFI fuse. idk what to do. i just ordered cat back system and high flow cat, will that make problem worse? also, i seem to hear a hiss coming from the engine bay near the wastegate. only happens when i take foot off throttle. this a normal sound? i only recently noticed it. thanks a lot and hopefully you guys can help.

The hissing sound is normal and its from the intake, yes. I have the same issue :)

The vibration could be from the motor mount or yes the intake itself. I always had a vibration problem though and a bogged down feeling even before the intake or any mod I did to my car.

It's either your exhaust manifold (I doubt though), intake, or your fuel injectors need to be looked at....also your motor mount, main cause of vibration.

hey thanks man, i was recently told that an AFC would fix the idling and bogged down problems. :D apparently after you reset the computer fuel maps like i had done, the computer just relearns the problem. so apex and hks offer afc's for like $350 and i guess its not an unusual purchase for turbos. hey, would you happen to know what a shimmed wastegate does? i here people talking about it. also, im thinking about getting a downpipe...how strict are people with them?

Have you done a BPU (basic performance upgrade) yet? That should give you a good around 60-80 or more HP/torque. Not sure how much it is...

Shimmed wastegate? Here is a pic of one:
http://home.earthlink.net/~gxstarchild/shimmed.jpg

what the hell is a BPU....so far, all i have is an intake, have a high flow cat coming and a blitz nur spec exhaust on the way. and by the looks of it, im going to be ordering the apex AFC. so whats that...maybe up to 250 or 260 hps? so how does the shimmed wastegate help?

Shimming the wastegate makes it open a bit later, giving you higher max boost pressure. Stock pressure is 6.8psi, but the CT26 is pretty efficient up to 14psi. Fuel cut kicks in at 12psi, though. Is the dump tube connected on the Compressor Bypass Valve? That might be causing your problem if it isn't or is leaking.