Check your fuel pressure. I had stumbling issues that I thought were ignition related. After monitoring the O2 voltage it was clear that the engine was leaning out at half throttle and then it finally threw code 44, lean condition. Checked fuel pressure, 7 psi at idle. Changed the pump, car runs better than it has in a long time, steady 14psi. I've had fuel pumps go bad on other cars but they never seemed to degrade before quitting. Perhaps it has to do with the fact that TBI pumps don't deliver much pressure to begin with, losing half it's pressure will still allow the car to run whereas with a TPI type pump, losing half the pressure would probably not allow the car to even idle correctly. Just thought I'd pass along this info to anyone who is chasing driveability issues past half throttle.
