i have a 08 6.7 with all the deletes and a smarty before the headgasket went i would never run over 200 on the coolant temp now that i have new arp studs and gasket fixed it jumps around from 180 to 205 back and forth ive checked to make sure i havent blown the gasket again and its good any ideas

 

Could very well be a sticking thermostat.

 

Sounds like a bad thermostat.

The stock 2008 thermostat is a 190° unit, it cracks at 190° ±3° and is full open at 207°. When they start to stick they will scream to 207°ish and then drop back down quickly, and often repeat.