leave the neg part along is my guess.
you make a grid on paper mark down 10 through 100 to represent the kpa in the injectors flow rate.
now look over your scan and look at what your maf kpa cell is and then note the ltft when in each kpa cell. ( 10 -100) lets say its -12 at 30 kpa. you would subtract 12 from that number in the injectors in kpa cell 30.
if it was +!2 you would add 12 to that number as per the kpa like above noted. once again. dont go the full number.
i will say i tried the full number's and over shot it the first time. go 3/4's the way. let the trims learn and re scan.
all this is in the manual i sent you in the webracing part of the manual.
