If your exhaust looks offset from the front, you need to line up the camgear from the back. As in follow the dotted tooth along its side and line it up from the back of the gear with the rear timing plate. Then you can line it up spot on, from the front because of the lean of the motor and whatnot its difficult to get it bang on.
I mark the inlet and exhaust gears along the side of the respective teeth and line it up that way, it helps get it right everytime. Your exhaust could be one tooth out, which i think equals 15 degrees of cam timing. It would explain why you've had to advance the base timing inorder to get it running better.