1988 Mustang Gt Random Power Loss

How's it going? I'm a newbie and just bought my first 5.0.
I've had this ongoing problem that when I'm driving it "cool" it runs great, and it'll drive great until i turn it off then back on... when i do this the car has no power just noise... it doesn't accelerate like it's supposed to. We've checked the fuel pump pressure and there is no pressure loss it was stable around 35-40psi i believe, MAF sensor is fine, throttle body/intake mani sensor seemed to be working, spark plugs semi new.. brand new wires, the timing belt was fine set at 10(idk what that is) so idk what's going on and no mechanic could really tell me.. and i also tried the OBDI but the scanner wouldn't even read the car.. so any help much appreciated..
I was told the car has these mods: t-5, hooker shorties, 3.73 gears, bbk maf, cold air intake and thats about it.. thanks in advance...wonder.gif