Below is the original post, but I'm hoping this will be a thread to help correct an erratic/inaccurate/unresponsive tach. From everything I've read it's a resistance value on a resistor 'pack' on the board for the tach that goes out of spec (small, white ceramic piece that looks like an IC chip). I'm hoping to fix mine, putting the details here (see page 2).
Well, seems like I'm one that needs one (others have said it's not needed). My tach isn't accurate, and I got what I almost positive (after online searches) is the tach filter from the same Monte the cluster came from. It's round with leads coming out each end (like an axial capacitor). I found a schematic for one (online here), looks like if this isn't one I'll probably just build one myself, simple enough.
If anyone else is looking for a replacement (one of the sites said GM disc. it) you can look here<i></i> (click Engine, then click Tachometer filter). These specific ones are on a Fiero store site, but I'd imagine it's the same part. If not, one of the resistors or the capacitor is probably just a different value. There's also a Corvette tach filter under the Electrical section if you prefer a Vette style one