I see a couple of possibilities.
One possibility is the "high performance fuel pump" is on its last legs. I don't know much about what aftermarket options are out there but I'd seriously question whether that part has been durability tested. If it is a GM-OEM part, its time to change it anyway.
You could also have a coil pack going flaky. They can go frustratingly intermittent before dying.
I just posted in another thread if you can catch your car doing odd things at idle, open the hood and unplug one injector at a time. You are disabling one cylinder at a time. If you just disabled a good cylinder the car will run worse and probably stall. If you just disabled the problem cylinder there will be no change. If they all test good or you can't find a bad one, then it is a system problem common to all cylinders and unrelated to injectors or coil packs/wires/plugs.
I doo agree with the suggestion to cruise by AutoZone and have them download the fault codes. This makes it so much easier.
Note that GM has no PCM diagnostics directly for bad/poor/too high/too low/NOK fuel pressure as of my best information, starting with the original TBI setups and all the way forward to the newest vehicles.