Hi guys, I've got a 95 WRX, relevant mods being VF34, 3" turbo back exhaust, Walbro fuel pump and Z4 ECU (15.65psi fuel cut). A couple of months ago I raised boost to about 16psi with my MBC and the car would hit fuel cut at about 4500-5000rpm at WOT, which was when it would hit the 15.65psi fuel cut. We fixed this by tricking the MAP sensor and putting a one-way valve into the air hose for it so that it would only detect vacuum but no boost. This has worked perfectly for the past month or 2, but now it's suddenly hitting fuel cut again... and I can't figure out why! I've swapped that one-way valve for a brand new one to see if it just broke, but it's still happening. I've reset the ECU in the hopes that might do something but it hasn't. I have a spare MAP sensor so I'll try putting that in next. It's just weird that it was fine for this long with the one-way valve trick and now suddenly it's not :/
Is there anything else that controls fuel cut from overboost apart from the MAP sensor? Is it possible to just run no MAP sensor? Any other ideas?