Here's the deal....around town the car (06 RS) drives great. Getting on the highway at 1/2 throttle with moderate acceleration, the boost builds fine to @15psi, then sputters. Wide open throttle, forget about it. The thing sputters at @10 psi or less and I have to let off. In other words, the harder I go the worse the problem!
( Stainless tube manifold, TBE minus the o2 housing(still stock), Short ram and hard intercooler piping, Dynoflash tune.)

 

check your spark plugs?

bad gas?

 

check IC piping couplers, i bet u find something...

 

boost leak?

 

I just changed them with no improvement and have had the problem with a couple of fuel refills. it sounds like the boost that I am building is just dumping out it a sputtering noise. The motor revs fine.

 

just read that you already changed plugs...

 

Great suggestion. Or at least I thought so until today when I changed all the intercooler piping and couplers to see if that was the problem! no change!

 

That will be my next step..I have an appointment Monday. Any other ideas to try in the mean time?

 

maybe u did not gap the plugs correctly