03 Tahoe driveability

[biggsteve97]

I have an 03 Tahoe Z71 with the flex fuel 5.3L. Last week going down the highway engine at operating temp going about 65mph when I pushed throttle halfway down to pass someone the engine stalled and the whole vehicle shook violently. It happened fast and it was like someone turned the key off then back on quickly. It happened two more times over the next 15 minutes then nothing until last night. Engine was cold only about a min or so after startup. When I tried to leave the parking lot it happened again. Only this was barely pressing on the throttle. Its like someone turned the key off then back on again quickly. This happened several more times in the next 5 minutes roughly about the same spot in the throttle. So I floored it from a dead stop and it took off fine no problems full power shifted fine. So I held it in second gear manually at about 35 mph and slowly pressed down on the throttle. The engine suddenly died. Right before the tach dropped below 500 rpm I managed to lift off the accelerator and the engine roared back to life. I have an aftermarket exhaust system so its very easy to hear when the engine stalls out or starts acting weird.
I have no codes or a service engine light. I have checked to make sure all wires are ok. I checked the air box, the filter, the maf sensor, all the connections up to the throttle body, checked the fuel pressure regulator, checked fuel pressure, even checked for leaks at intake, throttle body, and the injectors and found everything to be good. I did a tune up about 3 months ago and there was nothing abnormal about the old stuff and I used ac delco plugs. Fuel filter was replaced earlier this year as well as the fuel pump but that was for a sensor failure not for a pump failure. Does anyone have an idea what this could be. I really thought I was gonna be stranded on the way home last night.