I did the 98+ water pump upgrade recently on my 96, reused the single t'stat crossover with a AC Delco 195* thermostat. I also removed the radiator and flushed 14 years of farm dirt out. Since I did this, the operating temp seems to fluctuate between 185-195 on the gauge. I can watch the gauge move back and forth as I drive. It's not rapid, but it seems like the thermostat can't make up it's mind. I haven't checked the sensor to see if it's reading properly, but I didn't have a problem until I swapped t'stats. It hasn't gone over 195*, but it has been right at or below freezing here for a while. I used a Delco t'stat since I had read on here about the Stant having problems. Any ideas?