i have also this same hesitation actually recently just surfacing.
i cleaned out the injecters and used a carbon cleaner. thought it would kill a slight miss. able to hear miss pushing throttle just about 1500 rpm. i failed the emissions test w/high hc & co. i checked my egr and it was bad and replaced it. still have hesitation. checked plugs, wires, coil, control module, tps, iac ect........i checked all a hundred times. still have same problem....but there is a recall for the air injection pump. call chevy (for camaro) or pontiac (for firebird) and ask them about it. they will need ur last 8 digits of vin so have it handy. i have noticed that when i start it in the morning and start driving i have no hesitation, but when it turns off i start to feel it. BUT i am only speculting i really hope this fixes the problem.