Sudden Power Loss (opinions)

Well then we seem to be running out of things to check, that do both powerloss and a temperature change. Maybe you want to check your exhaust system for back-pressure.
EDIT
I do this by installing an 3/16 x 8 inch brakeline brazed into the exhaust pipe up into one leg of the Y-pipe. To that I attach a length of hose that allows a low-pressure gauge to be routed into the front seat area. Then I take for a ride. I find a long straight deserted road, get her up into second gear and give her a workout...... while watching the gauge.
Ideally, I want to see ZERO back-pressure, lol.
Typically I see 1.5 to 2.5 psi on a decent system, maybe 3.0 at most.
If it goes over 4psi, I want to know what's plugged. This might require moving the tap two or three times.
When finished, I shorten the pipes so they can't snag on stuff, but leave them in, and braze them shut.