UPDATE!
After procrastinating, being busy with work, and other excuses, I finally buckled down and got on with the problem solving...
The first thing was removing the triple carb Promax stainless steel braided fuel line. That fuel line and the large, single lower braided line was part of "what changed" from before when the engine was running fine, and AARRRGH aka after I got the carbs back from Promax and the engine ran really bad. To recap, I also changed the stock fuel pump to the
Carter M6903 mech fuel pump. New WIX fuel tank to pump fuel filter. Promax lower braided fuel line, Promax inline fuel pressure gauge, Promax reusable fuel filter, Promax upper 3 carb braided fuel lines, Promax jetable metering plates in the outboard carbs, Promax angled idle mixture screws throttle plate in the rear carb, Promax center carb metering block.
Problem was rough, down on power at every throttle position that was especially evident when I was on the center carb only, but very noticeable even at WOT.
Between the 3 Rochesters on my wife's GTO and the 3 Holley carbs on my car, and other prep for the 8 days of Cruisin the Coast, well that and the braided fuel lines being "new"
I didn't flush the lines out...
So I found a couple of tiny, hair shaped metal particles in the Promax inline fuel filter. Looked like
stainless steel BRAID CLIPPINGS. Yesterday when I removed the braided 3 carb fuel lines, I flushed them out with carb cleaner and here is a zoomed in picture of what I found:
So it looks like I really messed up not flushing the NEW braided lines, and after putting probably 400 miles on my car this is what was still left in the lines.
I took all 3 carbs apart (the reusable float bowl and metering block blue gaskets are AWESOME). Used carb cleaner and sprayed/flushed out every orifice and put them all back together, started it, let it warm up, checked for fuel leaks (tightened 1 fuel bowl bolt a little and that was it, it was leaking at the bolt head bowl hole) and called it a night.
Drove about an hour to my car club's annual car show, the first car show of the season, and
IT RAN GREAT!
The only additional tuning that is critical is a slight hesitation when I stand on it and the outboard carbs open. I never had that before under any circumstances. I guess I have to play with the jets in the metering plates. When I run the RPMs up on a roll and the outboard carbs open, it pulls hard, but I am getting a little pinging that wasn't there before so I'm thinking the new jets vs the stock plates may be a little leaner than the stock plates.
Thanks again for all of the help and suggestions.
My takeaway:
when you install ANY new fuel system parts, FLUSH THEM OUT!