Mine goes to 1/2 on warm-up then goes to 1/4 during morning. Afternoon, it stays at 1/2 in the afternoon.

Don't have rapid fluctuation on/off boost like you though. Hook up an OBDII scanner and check if the sensor is giving a wild fluctuation in temps. Remember Mav's water temp sensor situation & he lost 10hp on his NA?

Jesse

PS - why don't we have quality temp guages in our cars yet ?