please help me..idle issue.

[Javelin3o4]

Well one day the car just idled really rough and the car stalled, it sounded like it was missing. So it seems that when i first start the car it will idle fine, when it gets up to operating temp the needle on the tach will wiggle between the 500 and 600 rpm line. it sounds like the engine speeds up, then slows down again like its missing. I checked around the vacuum lines but it didnt seem like there was any leak I even disconnected and plugged the line going to the vacuum tank and plugged just incase the tank was cracked. When i unplugged my IAC connector it didnt seem like there was any change in idle/RPM, also when i first disconnected the vacuum tank line at the check valve it didnt seem like there was a change in idle/RPM there either I dont think its a fuel issue because i hooked up my pressure gauge and drove around with and the PSI held and did not fluctuate and when it seemed like the RPM's were jumping around at idle the gauge held steady. Its not throwing any codes either. I listed to each injector and all of them were clicking to show they were atleast pulsing. I've replaced the following parts.

1990 Firebird V6 3.1

Spark Plugs
Cap
Rotor
Ignition Module
Check Valve
IAC Valve
TPS
Fuel Filter
Air Filter
PCV Valve