Just a question searching back through this thread. Has anyone tried replacing the rad caps on the rad and turbo reservoir? I am just wondering if this might be related to crappy oem rad caps. Mine has a minor fluctuation from day one, but I've logged it via accessport and in traffic I've never hit above 190, sometimes it's dipped as low as 170 while cruising which is too low to be efficient.
Gurus that may read this, what is the sender for the gauge and ECM? Is it RTD or a bi metal thermocoupler? Transient changes that are fast can be picked up by thermocouplers but RTDs are slow to react but far more accurate. If guys are seeing transient changes that are fast but an RTD is in place the wiring could be crappy or the loop amplifier at the ECM has a problem. If it has a thermocouple than the issue could be air bubbles or a sticky thermostat.