Almost stalls when started

My 1997 Yukon with a 5.7 Vortec has issues again. Just replaced fuel pump and filter. Couple weeks later and now every time I try to start it it hesitates and sounds like it just barely starts. Like it will stall out. Sometimes need a couple tries on the starter. Then really low rpms for a couple seconds. The. It runs as normal. When it used to start after 1-2 seconds of starter engagement it would fire right up. Seems to have a slight loss of power on hills and idles slightly rough, but not very noticeable. These issues were both present before the hard to start issue. From what I have read it could be 1)bad egr valve 2)leaking or stuck injectors, 3)bad fuel pressure regulator. I just went out and picked up a fuel pressure tester. So u will check pressure, turn off key and see if the pressure drops. This should tell me if injectors are bad. I think? I heard to pull a vacuum line off the fuel pressure regulator and if it leaks gas while running or shut off then I know the regulater is bad. I think? Egr valve I just takeoff and check for proper operation. Watched a YouTube vid on that. Does all what I said sound like correct diagnostic procedure? Any help, advice, guidance is greatly appreciated. Last month I've done starter, fuel pump and filter and a u joint. Ran it for the last year with no problems whatsoever.