My friend just had his gauges installed. the gauges worked fine for about a week, and now the pyro is not working. The needle moves wherever it wants, whenever it wants. All the other gauges work fine, is the gauge bad?

 

If the wire to the thermocouple got in contact with the manifold it could have melted the insulation at that point. You would then be measuring the temperature at that new connection and not inside the manifold.

 

^true, the "sensor" for an EGT gauge is about as simple as they get, so the likelihood of it actually being bad is VERY slim. There is either a short somewhere in the wiring, or the gauge itself is defunct. If you can get your hands on a spare EGT gauge (it seems like I always have a couple laying around for some reason or another, so why shouldn't everyone else? ) you can test it out to make sure it's not the gauge itself.

 

Sounds like a poor ground to me. Make sure both connections are good and isolated from each other.

 

x2 on the ground. Make sure the ground is good before trying other things.