Yeah, 18° is too high. The timing you set with the spout out is the BASE timing. The computer advances/retards the timing based on engine conditions. Stock timing is 10°, though a lot of peeps can get it as high as 14° or 15° without pinging. I recommend turning it down to 10° as a test, see how it runs. Then raise it up by 2° and go for another drive. Keep going until you lose power or hear pinging (sounds like marbles in a can), then drop back by 2°.