Are you sure it's not running hot? Have you hooked up a handheld tuner to it and checked the coolant temp?
It's possible it's the stepper motor for the gauge, mine acts up but for me it's when it gets hot in the car.
I'd check the actual coolant temps first, then go from there.
300 stroker @ 11:1 compression, FRPP Stage 2 heads, 127300 cams, 4r70W, Kooks 1 3/4" lt's with 3" H mid-pipe, FRPP stinger mufflers, B&M ratchet shifter, UPR LCA's, JPC race UCA. E-Force TVS. Engine built by Everett's specialty repair, tuned by Manuel @ tudyno.com 9.98 @ 136.55 1.39 60'