They're finicky beasts. Seat of the pants can't compare to dynamometers, but I can sometimes tell the difference from one tank of gas to another. I stopped using Shell entirely at one time. Much later, I found out that Ohio doesn't regularly test the quality of gas anywhere, so chances are it was the fault of the one particular gas station, rather than Shell Oil.
The biggest killjoy is letting the engine idle in heavy traffic. It's so quick when it's cool, then it gets noticeably softer just after getting out of the traffic. Running it on the highway for a bit cures that. It just needs to move more air. The computer triggers the electric fan too late. (It's not the thermostat as I said before.) The computer can't be reprogrammed, only superseded with another, through the service port. That's done all the time by performance nuts, and I came very close to doing it myself, for this reason and for a better timing curve. Ford's is too mild, and they deliberately pull spark back based on speed, which is why cranking the distributor 4-6 degrees works as well as it does. Engine tech has moved so far past this, though. Everyone has a race engine anymore. Unless I'm going to go all-out, meaning tons of money, it's not worth the effort at this point. It was fun, though it could never touch my much lighter '85 GT with the same engine, better cam and pistons, and a massaged Holley 4-barrel carb. That was a dizzying quick car.
