hey, currently swapping a 325is drivetrain into a '85 318i body. Using the 318 instrument cluster. Tach sez 4/6 cyl. on a sticker on back. Anyone know how to modify it to work properly w/ other motor? There appears to be a potentiometer screw on it, do I adjust it there? If so, how? what? how much? ??? Thanks for any help!