I love driving this car i owe too much money not to drive it, i have a 2001 ford mustang gt with a few mods, the mods are pypes x pipe no cats, flowmaster exhaust, fenderwell cold air intake, i had a head gasket replaced on the right side now i have a hesitation bad and it shifts in to overdrive at 35-40 mph then sounds like something is holding it back but at wide open throttle it runs great, it seems like there is certain spots in the throttle it hesitates it drives me nuts i need help bad...........PLEASE

i have a superchips programmer but it is vin locked to my other mustang i traded in for this one i dont no how to change that so i can use it. 

If thiese problems only arose after the head gasket installation, i would take it back to the shop that you had perform the work to see waht they say. Those symptoms could be caused by numerous things.