2003 Gmc Seirra Stalling When Under Load

[gord-42]

my 2003 gmc seirra 1500 5.3 starts and idles well. Once warm it will drop rpm and stall at stops and when braking, restarts fast, idles well until put in gear. changed fuel filter, fuel pressure regulator,wires and spark plugs. when i changed the plugs i found the drives side where black and the passenger side were tan. Any help would be greatly apprecieated.

 

gord-42