The Tach in my 83 CFI, 700R4, Z28 Camaro is way off. the tach redlines when i am idle. there seems to be something like a capacitor mounted on the firewall behind the distributor it is in line between the tach connector on the distributor cap and the wire leading to the cluster. whatever it is it looks fried. My question is what is that piece and where can i get a new one. Also is it possible to just bypass it. I know it isn't the cluster because i have two of them (both stock) and they have the same problem. We have had no luck trying to find this part at the local auto store (advance Auto Parts) and the Dealer and still do not know what it is called.

 

Yeah this is a common problem for these cars, and the topic is widely discussed. Try searching to narrow down your answer, but I would look for a new tach or the capacitor that you need at a junkyard since I dont think these are manufactured anymore.