I have been scouring the board and FAQ for this exact condition and have been seeing some that are similar but not exact or the solution was for the Bosch ignition.

Bear with me as there are multiple situations here and will be looking at fixing all of them in the next few weeks but also need it drivable in the meantime between all of the fixes which will be done myself.

The cat went bad some time ago and had to install straight pipe where the o2 sensors are not hooked up, but also are not disconnected. This has worked for a year now with very little change in idle or fuel/air mix. Now that I have the new cat in hand, new headers and exhaust system ready for installation this weekend, the car begins to die on acceleration only... have to keep a very light foot on the throttle and it will pull away slowly... any heavy pressure on the accelerator will cause it to hesitate and miss and start to stall...back to light pressure and it will slowly accelerate through the 1500RPM to 2.5K/3K RPM range and then roars back to life and seems to run great until I shift the automatic transmission manually at about 4.8K. If I shift this manually at that point it keeps the RPM out of the trouble band and runs great until the next stop light or hill that drops the RPM's... ok runs good but definitely not full power, but well above a limp home mode.

This morning I unplugged the battery to reset the OBD and after just a little rpm bumpyness in the first mile, it ran like it did a year ago or better. Until 30 minutes later when the check engine light came back on and so did the symptoms.

Leads me to believe it is one of the sensors in the system other than the O2 sensor, but from these clues can it be narrowed down without a tester? Is there any way to keep the OBD in the default mode continously until I can fix all of this other than unplugging the battery every 30 mins?