if your temp gauge is bouncing then you need to bleed the coolant loop....a thermostat would not cause bouncing...it would be consistant...only thing to cause bouncing would be air pockets in the coolant loop...air cools and heats much quicker than coolant...if you have air pockets in the loop that could cause this....try bleeding the coolant loop....best of luck

How do I bleed the coolant loop. The coolant was replaced at the end of the summer with 2 gallons of MB coolant.

Would the rapid accelerations under load cause the engine temperature to raise quickly because
A: I am putting car under load and mashing throttle every time I pull away,

B: creating a miss/stumble/hesitation by accelerating rapidly or attempting to, that might raise engine temperature by itself ? If there was any type of preigntion or bad ignition would that not cause engine temp to rise dramatically ?