I have twin 500 EFI's and at 3500 rpm's and above I get tach bounce (needle jumps up and down) can anyone help me with what may be causing this?

I have cleaned off all the connections to the tachs and it still does it.

Check your connections at the ECM, have seen this problem accouple times. When your out at the lake next time, at idle open your hatch and wiggle the connections and watch to see if your tach bounces.

Also check for plug wires touching any wires going to the distributor or knock sensors.

Dave

Thanks guys I will check these out.

JB