I have a '89 IROC that I just bought about a month or two ago and the Tach is way off, it says I am idling about 2,200 RPM in Neutral, and it is maxing out (7,500) when I acclerate. Just wondering if there is something I can do to fix it or if I have to get a new part, I don't want a tach that is not in the dash, I want to keep it looking pretty stock.

 

Theres a documented fix for the innaccurate 89 and older tachs here on the boards. I believe it was posted by a member named Morley. Try doing a search, you should find it without too much trouble.