[Red Mustang Gt 46]

Try a different brand of gas...

Undo the battery for 30 minutes and reset the computer. Drive normally with some highway miles for about 20-30 minutes to let the EEC adjust to new settings. (I mention this because you said you cleaned the MAF sensor)

Timing is varied by the EEC based on conditions of the air, temp, shifts,...etc...

I wouldn't worry about it...