96 1500 hard start when warm
 

My 96 Chevy starts up right away first thing in the morning but once I drive it and try to start it again its not as good takes a few tries. I've changed spark plugs and wires, cap and rotor, fuel pump, fuel filter, and pcv valve. Actually it started doing that about a week after I replaced the ecm. I would appreciate any help I can get.
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