Egt
 

A couple years ago I put an egt gauge in to monitor it while towing the fifth wheel, now sometimes it pegs over to the highest temp reading on the face. No loose connections seen, would this indicate a bad gauge or sender?

Possibly bad amp box or probe is going bad. Normally the gauge itself is fine.

When mine did that it was a bad connection. It was kind of corroded and just wasn't making good contact. I found this after I had already bought a new probe. Recheck and clean ALL of your contacts/connections.