Help please! Strange power loss problem

I have an 88 Camaro IROC 350 TPI that I am having a weird loss of power problem with. For the first 5-10 minutes after I start the car, the car accelerates awesome, no problems. However, after 5-10 minutes, I hit the gas and there is very little power. If i shut the car off and immediately start it up again, the car is fine for the first 5-10 minutes, but then again after 5-10 minutes, major loss of power on acceleration. There are no problems idling, even after 5-10 minutes. There are new plugs, fuel pump, fuel filter. Rebuilt tranny this week. Changed out the coil. Didn't do it. Checked cat-it is already all cored out, nothing in it. No muffler. No engine codes being thrown. What is goin on here? Could this be a lack of back pressure problem with hollow cat, no muffler?

So i measured the resistance at each fuel injector (one probe on each injector prong right?) and the resistance for every single one came back at 6 ohms. Does this mean they are all bad? Would the car even run?

I'm not sure I'd attribute the power loss to the resistance of the injectors. It doesn't make sense to me why you'd be able to turn off the vehicle and immediately restart it while warm to get another 5-10 minutes of power if that were the issue.

However, there may be forces at play here that I don't understand.

Yeah, this is what baffles me. I mean, i thought the injector resistance was supposed to be above 12 ohms, but every one is at 6. Could I be measuring wrong? Wouldn't i have a problem all the time then?

OK, so i don't think that the resistance readings for my injectors i posted earlier are correct, as the multimeter I was using was pretty shady. Plus, I can feel them all pulsing when I am having the problem. I checked by TPS, and that seems to check out. I unplugged by O2 sensor and that didn't make a difference. This is baffling because if I shut the car down and immediately start it back up, it runs fine for 5-7 minutes. ?????

OK, so today I ran the car in Field Test Mode (Jump pins A and B on the ECM after the car is running). It appears that my car is constantly changing in between open and closed loop modes sporadically. ????