We had this car in for a few days now. Originally came in with a throttle position sensor fault and boost problem. TPS has been fixed.
The car is boosting to about 5psi until around 3500rpm and peaks at about 15psi at 4000rpm. Codes for IAT, MAF ,MAP were on but no EML light. Codes got deleted and nothing came back. Undid the battery to see if resetting the ECU did anything and then put it on the dyno. It boosted too 17-19PSI at 4000rpm nicely((ish) more or less a diagonal line). Next run it dropped about 1.5 PSI between 2600RPM and 4200RPM. So did the next run, and the run after. Always between 2600rpm and 4200rpm. MAF and MAP were replaced. No change. Reset the ECU again and it regained its boost. Did some more runs and the same happened again. Kept loosing boost between 2600RPM and 4200RPM. all runs made between 190-205BHP (at about 5000rpm, no matter how much boost it lost in the mid range all the runs caught up to its best run and got close to its best performing power)and an average of 207 lb/ft.
MAF or MAP isnt showing anything strange. No EML light, only service light. No smoke, hesitation or misfire. Boost control Solenoid seems to be doing its job. Actuator is holding positive and negative pressure just fine. No boost leaks. Car has a receipt from REGAL but no dyno run print or proof of remapped power gains.
2007 Corsa (D) VXR, Pipercross airfilter and decat.
Any help or advice would be greatly appreciated. Thanks in advance.