i'm stucked , help me !!!!!

[dimebag]

Hello

car configuration:
-woesner pistons
-big cobra
-stock turbo (until soon)
-giant green injectors + 3.5b press regulator
- 3'' downpipe with catalysor
- 3'' hirsch exhaust
- DO88 intercooler with pipes
- RXP 251l/h fuel pump
- modified airbox with maptun filter
-biopower ecu tuning (320hp, 450Nm)

This is the situation:

My 9-5 aero (2001) have boost or so issue, i explain.

When i drive, everything is ok, if i suddently accelerate , the turbo needle goes directly into the red zone, perfect, but after it go down to the limit of the red and yellow zone (bad...).

Some time the car have vibration (missfire) when torque is needed and boost goes away....

I have change the fuel pump this morning, it already have a Walbro 255l/h, i suspect ir because when boost goes, the sound at the exhaust was like a dirty carburated engine at WOT, sound like someone spit inside the exhaust.

since i have change it i do not have this again, but the boost is never the same.

I have done the BPC bolt mod without any change....

I have change the DI K7 for an OEM from neobros, same , change the catalsysator for a mpatun downpipe, same......

i'm speechless.

any clue ?

Cheers

Laurent

[GeoffR]

I suggest that you check the vacuum hoses (3mm or 4mm rubber hoses) also check the bypass (dump) valve for leaks. Any air leaks can cause problems and the higher the state of tune the more effect they have.
When did you last change the plugs and what are they, Saab recommend NGK, anything else causes problems. The hand book should tell you exactly which ones but apparently tuned cars need the non-Aero plugs and regular replacement.