It is IMPOSSIBLE to read plugs to indicate part throttle A/F ratio to your engine.
This new fuel makes it even worse.
The only way folks used to read plugs with any sort of accuracy, was to make a full throttle pass, then shut the engine down immediately after crossing the finish line, coast to a stop, then pull a plug and look at it.
Even doing that was a poor indicator of what's really going on....IMHO. I say that, because any idling at all will blacken them right up on most "high performance" engines, as they use big cams with lots of overlap, so tons of unburnt fuel finds it's way thru the engine at idle and low rpm's.
Tune at the track by ET and MPH, not by reading plugs.
Tune on the street by setting the idle mixture screws for best idle quality at the leanest settings, best fuel economy, etc.
Tune the part throttle by driving the vehicle, and evaluating throttle response, smooth off idle, smooth/clean power for "normal" driving situations, and good power without any surging, flat spots, or too much throttle angle to acheive vehicle speed(s).
Tune the full throttle by best power production, either by engine dyno, chassis dyno, or drag strip ET/MPH.
"Seat of the pants" testing will get you close, but ultra fine tuning needs some sort of measuring device(s) to know when it is perfect.
I would also mention here that Q-jets are very efficient at light throttle openings. If you saw the plugs from my engine, they are clean, and light tan to almost white. The carb and distributor are in perfect tune, and the engine performs flawlessly in all areas.....Cliff
