90 camero and the tach is off. always reads to high. what does the tach on these cameros run off of

Camaros use the negotive coil side.

$20 says its the tach guage itself.

www.thirdgen.org (http://www.thirdgen.org) and search in the forums for it. I have a bunch of posts in there too about it. To fix it you have to solder in a resistor but you have to find the right resistor value first.