simple terms for maf- you are basicly comparing the actual air flow that is comming through the maf in hertz vs. the projected amount by the pcm. Bigger tb's cold air intakes ect can affect your maf tables and cause them to be off.
Basicly you open up your scanner to the maf hz histro and drive around trying to hit all of the cells.It will be giving you numbers like -5 and +5 in all of the sells that you hit. (this is the actual amount that the pcm is pulling/adding from this cell) after all of the cells are hit on the histro on your scanner you open up the editor and copy the maf table from the scanner to the editor by clicking copy-paste special-multiply %. you have to do that about 3 times for the maf hz histro table in the scanner to come up with all 0's (not adding or subtracting fuel from that cell)
Without a wideband only do maf hz's from 0 to 7500hz's
Example- if in cell 7500hz on your scanner in you maf histro you have a trim of -5....When you copy-paste-special -multiply by % it is taking that -5 that you pasted in there from your scanner and multipling it by that amount(actual airflow) vs. the (stock value) amount that was in the pcm. Wich would make your fuel trims zero in that cell.
GEt it?? ok so it's not so simple lol
If any one has some questions let me know and i will try to explain it better
