[djmtsu]

It is the sending unit. Mine did the same thing after the engine swap. When I took it out I noticed a slight ding in it, that is all it takes for it to act up.

Unfortunately for me, however, I left it connected during testing and initial start up. The gauge was pegged out and finally, it actually broke. So now I have an Autometer sender in the factory location (using an adapter from BSPT to NPT) and the gauge is above the stereo.