[Early TBI systems were designed with a number of redundancies. One of these is found in the ignition module. If the module is not in EST mode then it will very quickly ramp up spark advance when RPM reaches a threshold. There are different advance amount and different rpm thresholds based on the module part number, but most of the behavior described above should be considered normal.]

Copy that. I am comfortable with this now and I do see the repeatability at the threshold rpm as would be expected.

[What is not normal imo is the report that spark advance changes during backfire. Unless this is happening at the rpm threshold mentioned above, I would be tempted to investigate the aftermarket ignition parts. Is the rapid change you described what you were referring to by "jumping?"]

Agreed and I plan to still investigate this weekend. The jumping I was referring to is related to the dip in timing at the time of backfire while the EST is disconnected and the erratic behavior while the EST is connected. Erratic being the not-so-consistent retard values when accelerating at idle. That being said, I have only watched the timing with a light and I have not looked at it since I bumped the AE vs MAP values and smoothed the spark table. The adjustment seemed to attenuate the exhaust backfire and smooth out the throttle some. BUT that was one 20 minute session. Just enough to warm up, tinker for a minute and shut down for dinner. Should have more time this weekend to validate the improvements. My gut tells me it is likely related to the tune at this point.

[The values in this table represent injector "on" time. Larger values turn the injector on for a longer time, delivering more fuel. That engine will want much more fuel during acceleration enrichment than a stock TBI. I expect you will be working on the VE tables considerably as well.]

Copy that. Matches up perfectly with what I had in mind.

[If you have dyno software or a simulation for your engine you may save time using the shape of the torque curve to rough out the shape of your VE tables.]

I like this plan a lot. Sadly, the last time I ran Desktop Dyno it was on a floppy drive. I have been thinking about procuring a copy of the new program though. I have about a bajillion dollars wrapped up in kids video games. What's wrong with a little fun for dad right? Meh. we'll see.....that first program was really helpful to me back in the day though.

[If that Grumpy is the same Grumpy I knew, he was a very creative thinker with many good posts. If you can find some of the early ones they are likely to get you thinking about EFI and engines in ways you hadn't previously.]

It may very well be. I have read his and others posts till my brain was smoking considering what to do with this engine. Very insightful and he was good with relaying that very technical information in layman's terms. With a huge amount of resources. Huge. Truly dedicated individual as far as I could tell. Sadly I never knew him. But what a wealth of information. For real. I work in a very technically oriented field and the only way I can decompress sometimes is to read about other very technical but unrelated information. This site and TGO has been great for me. Truly appreciated.