Vortec hesitation what's a

Thanks for adding me. I have a 1996 Chevrolet Cheyenne C2500 2-wheel drive 5.7 l vortec VIN code R pick up I'm having a hesitation or misfire problem at driving speed but it idles perfect. Just replace both heads because they both cracked even though the truck has never been hot a day and it's life. Even with the heads cracked the truck ran perfect. Got it back from the shop has this problem I'm speaking of and I've taken it back three times now new spark plugs new cap and rotor obviously new heads all of that. NOT ONE CHECK ENGINE LIGHT NOT ONE OBD2 CODE!!! I don't know what there is left to do. Seems not to hesitate as much when it is cool and the winds and has not warmed up once it has the hesitation is there between 1800 and 2500 rpm I haven't pushed it above that but even under load it is a steady as a tatian. EGR I checked thoroughly and it is operating as it should. No vacuum leaks I'm at wits in here if someone is ran across this problem before please help me out!!!!!!at the shop we put they're very expensive computer on and drove the truck around and it did not record anything that was out of the ordinary the computer says the trucks running fine but it is not.

Possibly the distributor gear has play in it causing the misfire. Try look at cam retard on a scanner if it bounces around that’s the issue.

don't overlook a possible fuel delivery problems... check your fuel pressure readings. Weak fuel pump can provide adequate fuel at idle but not at higher RPM. Check fuel filter and pressure regulator as well.

Also make sure grounds are good. I had a few that fuel pump pressures were dropping at high rpm n found ground on firewall to be bad

Great call. Also if it has the spider injectors they are known for the poppets to malfunction. The fuel pressure regulator is inside the upper intake manifold... they tend to fail and leak causing probs... so if its the CSFI " spider injector system... upgrade to the MFI " Multiport Fuel Injection.
Good Luck !