Tach is very sporadic

[jersygsx]

The tach jumps all over the place and on full throttle it will shoot back down to zero. I have tried gauge clusters, I have tried a new ecu, I looked at the plug on the back of the intake manifold, it was plugged in. What is my next step?

 

[skinnyt]

check your wires.

 

[jersygsx]

From the ecu to the coil pack?

 

[skinnyt]

start from the gauge and it will work its way back to ecu.