Help!!! Bi-monthly stalling has increased to Bi-weekly!

Where to start.. It's an '89 IROC LO3. It runs awsome 85% of the time. It idles around 600 when in drive. Sometimes, the idle gets real rough and then it just turns off. It usually starts right back up again without issue and runs fine from there.

This used to occur once a month or so. Now it's once evert 2-weeks. I thought it was due to heat, but last time, the temp gauge only read about 160.

I have replaced the EGR valve, EGR solenoid, IAC, oxygen sensor, ign. coil(w\MSD GM), installed a K&N Open air, and installed a Hooker Cat-Back with new high flow Catco cat. I even replaced the alternator and battery. No codes are being thrown. The dang thing still stalls periodicly.

The last thing I want is to be sitting next to a blond in a Mustang, laughing her a-- off lookin' at me. Just kidding on that part, but Can anyone help???

I appreciate any input. Thanks.

Andy