So for the past couple of days my Saab has been stalling out. I replaced the plugs and DI cassette and the car feels like it hesitates and wants to stall again. I do have an exhaust leak and I have the turbo fuel rail and FPR in line but I have been running that FPR for about 9 months now.and it's just starting to act up. I'm thinking I may have an oxygen sensor problem so fuel is just being wasted but I need to make sure. Any suggestions? I am running a N/A 9000 with an exhaust Turbo fuel rail and fuel pressure regulator a turbo MAF meter and an intake. Keep in mind that I've ran this setup for a really long time now.