Ok, third post. After 3 very frustrating days, I realized I did the return check wrong. I checked flow out the return to the tank, so it was total return fuel (about 160ml/15sec.) So I was about to test return flow from each bank of injectors. I say about too because after 2 days of NO DTC's all of a sudden I get a P0090 code for fuel pressure regulator. At this point I'm not sure what to do, certainly don't want to be a parts swapper, but I'm not sure where to go next. To begin with I'm going to clear the code, do a batt disconnect and start the DTC process over. If anyone should have opinions I would love to hear them. I will follow up with what I find.
Thanks

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Here is the current info I have received on this situation. It comes straight from the GM people. Apparently if a P0090 code (fuel pres, reg.) exists with a no start situation the ECM needs to be replaced. Has anyone else had this problem? Any GM techs want to chime in here? I get NO other codes.