Hi every one I’m having a fluctuating problem and im hoping you can help

Basically 99% of the time my 95 (260ps) wrx is running on 0.7 bar it runs rich and slow, also the acceleration and boost builds gradually. not impressive or enjoyable at all 1% of the time it runs grate it hits the 0.8 boost target (z4 ECU) the turbo spools fast the car pools really well the boost kicks in early and hard pushing you in to you seat (This is the car I expect and love)


Unfortunately I am at a lose as to why. I have a few questions that might help me diagnose the problem

I have been pointed in the direction of my MAF. But I read somewhere that on WOT the MAF reading is dismissed and it relies on the map sensor for manifold preacher insted. Can any one confirm or deny this?

Would a faulty MAF cause this on WOT or would a faulty MAF trip limp home mode with no errors before I get a chance to floor it


What I have tried
I have checked for leaks and returned the car to the factory recalculating dump valve. Unfortunately it is still running a cone air filter as I have no standard air box.

The car will stall if I disconnect the MAF. It thinks about it for a few seconds, splutters then stalls.

To test for limp home mode I reset the ECU it shows no errors and was inconclusive. I reset twice and once I got full boost for 1 mile then it went back to low boost and the next time I there was no change

I changed the spark plugs to NGK PFR7B and reset the ecu at the sane time as changing the dump valve to the standard one. it ran perfectly for the hole weekend I parked it on Sunday and didn’t drive it again till the following Saturday by then it had gone back to low boost and running rich.

Coil packs look questionable but I don’t know if it would affect boost levels like this