i really need some help/advise for my 95 gt

[larrylass]

I have a 1995 mustang gt 5.0 motor and did some mods recently; trickflow street heat intake with a 65 mm throttle body. bbk shortys with a bbk x pipe.when i drive the car it will run perfect for about 3 minutes and then it starts to mis fire horribly and detonate.when the car cools off the same thing happens again. WTF ive changed throttle position sensors twice and set the voltage from .90 v to 1.00 v. i know .97 v is ideal and this is where its set. the EGR is unhooked along with all smog related parts. they were all un hooked before the mods and the motor ran fine. ive also changed the IAC twice not that that would do anything and my o2 sensors 3 times. I just cant figure out why the car starts to misfire and detonate after 3 minutes. Ive also cleaned the mass air meter 2 times with a non clorinated brake cleaner. Im just at a loss and need you guys help PLEASE!!! ps yes all the plug wires are on correctly

Thanks
Larrylass