Hi Paul,

I guess I’m back at you again without any more suggestions.

On Dec. 8th I ended my post with a last second thought about the FPR and my reason for dismissal as a candidate but I did add other symptoms can occur.
They are not so pronounced as an acceleration issue but the FPR does affect cone patterns out of the injectors. With the breathing of the cam “coming on line” this may be more crucial than I give it credit for!
Definitely something to archive in the ole’ memory banks!
In the carburetor days these symptoms were called a flat spot with the jetting or an accelerator pump diaphragm or leverage adjustment.

I believe you were also chasing the idea of fuel pump check valves or the in tank pump being weak.
With all that going on I assumed the FPR or fuel pressure was already looked into.
Guess it was but disregarded by you as well by being reminded by looking at your backup in the trunk. It probably dry out back there in the heat. Not the place to store one, I’d say?
It must getting fairly regular in faltering, that the momentary install, took it away! That is a good to have things work bad consistently, because with intermittent troubles, they are really frustrating!

I sure hope it works out.

Phil