I know I baby the crap out of my truck, it's the first vehicle I've ever had since new.(got it with 17 miles on it) I probably give that truck 3 times the attention that it needs. So I think I know how you feel, OP.

If the new ECM doesn't change the picture, pull the distributor, and check the distributor cam gear.(at the distributor base)

Then it would be time to pop off the timing case cover. First look to be sure you have no broken timing gear teeth, regardless of the quality or type of the gears.
Then carefully inspect the timing chain for stretching.

Then bring piston #1 to TDC, and make sure the timing marks on the gears line up.