I dont have a muffler at all, and the tailpipe is really short- this makes for ALOT of whine.

 

3" tailpipe after turbo here, no cats.
The tailpipe quiets it down a lot but does affect spool. When I had the tailpipe off last fall you could definetly notice a performance diffrence.
Spool speed and HP were down noticeably. I would run a 4" with a muffler or resonator or both if you want no restriction and a quiet system.
Maybe a 4" Duramax catback modified would do the trick.

 

i have hi-flo cats, i wanna take them off but i dont know how would it affect?

 

It will get much louder for starters, better spool up depending on your turbo size.
You will need a re-tune and have to shut off your rear O2 sensors, that is if you can pass emmisions without the cats.
They don't do emmisions where I live.

 

ill try doing all this stuff next weekend

 

Because the turbine is an expansion chamber. The more heat it can extract from the exhaust gases, the quicker and faster the wheel spins.

There are two components that impact how effective the turbine works (which in terms obviously impacts the compressor). The temperature differential across the turbine and the pressure differential across the turbine. You want the exhaust gases entering the turbine as fast and as hot as possible for maximum performance. You want to the exhaust on the down side to be as unrestrictive as possible.

 

thanx, thats really helpful, so i should either put the stock manifold or wrap the headers til the turbo

 

Stock manfolds AND wrap it back to the turbine...

 

i dont have them