I have been trying to fix my tach bounce at high RPMs (>2700). Below 2700 the tach is dead on with my engine analyzer. To try and solve this problem i did the following:

• swaped tach circuit cards,
• put in a new tach filter,
• did the resistor mod on the tach resistor chip on the circuit card,
• Tested the ignition module (at Autozone).
• replaced condenser/capacitor inside the distributor
• replaced the plug wires to ACDelco wires.

Well there was nothing left to change except the ignition module. So even though it tested ok at Autozone I bought a new ACDelco one. IT FIXED the PROBLEM.