Rough idle , ran many tests

[migs_auto]

1994 mustang gt, won't idle when cold, very rough idle when warm, sounds like it has a hi perf cam but it does not. Rough running even up to 2000 rpm, like it has a miss. Car has headers and a farly new exhaust with hi flow cats and new o2 sensors last year. It started running rough about a month ago with a gas smell and found fuel pressure regulator leaking. Replaced regulator and schrader valve. Set pressure to 48 psi but still idle'd and ran rough. Set timing timing to 10 deg btdc with spout off. Key on engine off shows no codes, key on engine on test also returns no codes. Ran a cyl balance test and first try returned 3, 5, 8. Cleaned spark plugs and distro and ran it again, this time we get a 90 (all cyl pass). replaced the iac but this did not help. Next test will be vacuum and compression. We did remove and reinstall upper intake while tracking down the gas smell. Any ideas to try would be greatly appreciated.

[migs_auto]

Mods on this car :

Cold Air intake with after market 70 mm 19 lb MAF.
70 MM throttle body.
shorty headers
less than a year old hi flow cat'd h pipe with o2 sensors replaced at the same time

Car ran fine with those modes up until a few weeks ago

IAC is new but probably didn't need replacing, cleaned MAF with MAF cleaner, throttle body clean. had to replace a few vacuum lines when re-intalling upper intake. New fuel regulator set to 48 lbs (using a FP gauge attached to schrader valve)

[migs_auto]

Vacuum varies between 14 to 17 in as the engine speed varies between 900 and 1200 rpm to hold a very rough idle. It seems like it is getting worse. Added some new gas today.

[migs_auto]

Tried isolating vacuum by sealing off all three vacuum outlets from the intake manifold. Car ran exactly the same. Interesting though there was no code generated from running this test. I am now thinking maybe the PCM is bad. Seems like we should have gotten some kind of code.