I have a D15B2/Z6 mini-me and a D16A6 having the exact same issues at the same time. Neither can seem to make it to redline. The problem is this. Whenever either car is under hard acceleration, once it gets into the 4k's, they begin to sputter as if not getting enough fuel. The tach jumps and skips and the car just won't go more and sometimes backfire. They both do the same thing. The mini-me has given me the Fuel Supply Code and the A6 has given code 1 - Oxygen Signal output. Has anyone had these problems or symptoms? What could be a fix? High flow fuel pump, fuel pressure regulator or O2 sensor? Or is this there something else I should check? Thanks guys