i have replaced the lifters, intake and exhaust valves. lol i dunno what else it could be. Theres something i always think about. this problem with the 90 Z's where they had trouble with the lifters. i dont know too much about it but always wondered if thats what the problem has been the whole time. if someone could explain it fully, and help me figure out if thats what is my main ticking problem it would be appreciated very very much!