I have a 2001 Suburban 1500 4x4 with about 120,000 miles. For some reason it has a hard time starting, especially after a long trip when it gets up to temp and sits for about an hour or so. It cranks fine and strong but for a second or two after cranking it starts but you can tell it was a rough start (almost feels like their is to much fuel because i feel a sputter). I searched and pretty much every item most people have an issue with that would cause this has been replaced. Let me give you a list:

New parts:
Fuel Pump (Left me at the side of the road, now pressure at the test port is @ 55 PSI and holds steady)
Fuel Pressure Regulator (even though no fuel came from the vacuum line, figure I would replace it for $60)
Fuel filter
Spark Plugs
Wires
PCV Valve
Battery

The last thing people seem to be having an issue with was:

1) Fuel injectors
2) Dirty valve train or lots of carbon build

The truck idles fine when it is started so that leads me to believe the throttle position sensor and MAF are fine.

Modifications I have on the truck are:

Magnaflow exhaust
Magnaflow Y-pipe w/ highflow cats
JET Stage 2 ECU piggy back unit (says I need 91+ octane but have been putting in 89,not sure if this could be the cause, but I did run 91 on a recent towing trip and it did the same thing after we stopped at the hotel)
Volant cold air intake


Anyone have any tips or ideas, I am stumped....