I had posted this problem before. I had a clogged exhaust system. I changed out the cat and idle vacuum went from 15 to 17.5" Hg w/ a/c off and from 10 to 14.5 w/ a/c on. Is the loss of vaccum with the a/c on normal. I stiil have warm hesitation when the car is warm. It's almost dangerous. Compression test low but normal, new ignition coil, wires, rotors, etc. Fuel seems like where I need to go next, I think????