Just got back from a 3 day event at NJMP with the BMW club. A lot of fun despite missing a few sessions to two cracked brake rotors... There was a Mach 1 there, and we ran south jersey parts stores out of rotors. Next time I'm bringing four spare front rotors!
I used the SCT to remove 2 degrees of base timing, and changed WOT a/f to 10% rich. That seemed to improve my power. I will do a log of this setup before changing anything else.
This week I will perform a compression test, and will swtich the plugs and coils bank to bank to eliminate them as a problem. After that, I may swap injectors bank to bank. The guys out in AZ at Bondurant think that its an intake manifold leak, and I should update to a newer plastic/aluminum intake.
MAF was clean, sprayed with solvent, and graphs did not change. Only the stock paper filter has been used. . Cats are almost new, high flow from jegs or summit.
My understanding is at WOT, computer is in closed loop mode.
I don't hear an exhaust leak. I don't know how an exhaust leak would cause a reduction in MAF readings.
I don't recall if I checked TPS, but I will. TPS would affect both banks I would think.
No oil burned, and I only run FLAT OUT!
Car has 9000 miles. I don't recall if we changed the O2's when we got the car 3000 miles ago. The O2 sensors seem to be working perfectly, since they I have done multiple WOT pulls, and the O2 sensor logs look the same.
My newest thought is that I'm losing spark on one of the bank 1 cylinders around 4000rpm. This is causing the engine to lose power, and sending extra oxygen to the bank 1 O2 sensor. That would explain a lot of things, and the computer would show 'lean' since there is uncombusted air that hasn't had it's oxygen used.