So many on this forum have asked if there were a lower-temp thermostat available but not so low that it'd cause the ECU to go into "startup" fueling mode. This should do the trick. It's compatible (in fact must be used) with the Mercedes-Benz 1132030275 thermostat housing (that's the OE Crossfire thermostat/housing gents!). The OE thermostat is 188.6F so your car should run about 9 degrees (F) cooler.
https://www.vrpspeed.com/product/mmts-mb55-03l/