Timing Jumps in ESC Bypass Mode and Rough Idle when Warm

Folks,
I have a post in the C/K Forum about an issue with My 90 GMC Sierra. All of the details are in the thread below.

http://www.automotiveforums.com/vbulletin/showthread.php?t=630067

If anyone has some insight on why the timing is jumping even when the ESC is in bypass mode, I would appreciate it.

Thanks,

2000CAYukon

UPDATE: Problem is now fixed. Read post above for more details!