my 97 impreza import sti, mods decat and airfilter, once warm and boosted quite hard a few times, vehicle jults violently on high boost and engine light comes on, then goes out after a few minutes of cruising speed, previoulsy had a gems ecu fitted but standard put back on, ive cleaned the boost controller on the osf wing panel and vacuum pipes off this to the turbo and inlet manifold, has a standard recirc d/v too, not sure where to go, because its not all the time, and whether a new ecu and programme would benifit.
advice would be bludy helpful as im too scared to drive hard.

 

Sounds like its hitting the boost limit/boost-fuel cut. Its a pre set safety device on the car to stop you overboosting.

The gems ECU probably had a higher fuel/boost cut off point meaning you could have more boost, eg: if the limit on the gems was say 1.5bar the fuel cut/boost cut would be about 1.6bar.
The standard ecu limit is probably 1.1-1.2bar and fuel/boost cut would be approx 1.3bar.

With the decat and other mods the boost MAY have risen slightly as now there is less back pressure and more boost flow

I think

 

I don't mean to hijack this post but I think I have a similar problem. I've noticed now on occasion when driving hard when I let off the boost it jolts fairly badly which it never used to do. I lost my map setting after an engine rebuild however I still have the Walbro fuel pump fitted. Could this be the cause?
Thank you.

 

Lost your map settings. What ecu you running and what other mods you got. Does it only jolt when letting off boost, do you have a vta??

 

ive now changed the restrictor pin in the vacuum pipe bigger opening, went really well for bit then once boosted hard 5 or 6 times bludy jerked again! not sure what next, its only decat and induction filter??

 

boost gauge fitted, all vacuum hoses replaced, running 0.9 bar at about 3500 to 4000rpm then creeps to nearly 1 bar at about 5.500rpm, just wondering could it be the boost sensor?? just seems electrical as it happens intermeadiatly, i was booting it for quite a while the other day was fine! then turned it off for half hour went back out booted it a few times and happened again, possible actuator mayb? really frustrated now