Losing all throttle control?

I have a 96 mustang gt. Runs great during early morning and late night in the cool temps ( i live in arizona) but when i drive it in the middle of the day it will be doing fine, but then out of no where i will get no response in the throttle floored or not. then when i pull over to stop it acts like its vapor locking which is impossible cuz its fuel injected.. but it sounds like its starving... ive replaced pretty much all temperature related things.. only things i have left are FPR, Fuel pump which i replaced in december but i guess could be intermitently going out? MAF which seems to be working properly. Im running out of ideas.. if anyone has any input that would be great. I am replacing the FPR today.

Has a new batterry. when i put in the battery inspected all terminal wires, and cleaned all terminal attatchments and added corrosion pads. Alternator is putting out 15 volt. new serp belt. Cleaned maf sensor. new vacuum lines. no air leaks check it. new FPR. put on a new fuel filter and fuel pump screen when i replaced the fuel pump. New spark plug wires. and new spark plugs.

I did the fuel pressure regulator this morning and to do it you have to de-pressurize the fuel system. and to do that you unplug it from the inertia switch which just kills the pump entirely. Then your to start the car and burn off any excess in the system. (which was told by my chilton book). Doing this i discovered that i got the same exact symptoms i have been having with the fuel pump disabled. So im pretty sure i got a faulty pump back in december. I will replace the pump tomorrow. And if that does not fix the problem im thinking it will be the inertia switch going out.

has a new TPS. But as i said i did drop the tank and replaced the fuel pump, but when i dropped the tank i have come to find out that the inside to the old rubber gromit for the fuel neck, was still in the fuel tank. So the person i had helping me the last time did not pull it out like they had informed me. so im guessing that this was just sucking to the fuel screen and causing to not to get enough fuel. i havent really put it to the test but im pretty sure this is why it was all messed up. thanks for all the input guys