My greddy egt gauge has been acting funny. Occasionally the needle will wobble. usually between 3-400 C. The peak/hold functions work without any wobbling. It doesn't happen all the time. Today it happened around 700C. I am wondering if the probe is going bad. i have it tapped into the casting button on the drivers side manifold.

Take it out and look at it and see...

What am I looking for? What would indicate that it is bad? Hunks missing?
Thanx.

It should be fairly obvious if the end is melted/slagged/missing.
There may be an electrical method of testing it as well with an ohm meter or some other testing method, but you would have to contact Greddy or your vendor for specific information concerning this.