<<One thing I did notice after changing the thermostat was that my temps run cooler than they did prior to changing the thermostat (82-85). It could be that the thermostat was marginal, but I rather think the lower running temps are due to the fact I replaced the coolant with a 40/60 mixture instead of 50/50. This of course should cause the engine to run slightly cooler with the reduced amount of antifreeze in the system.>>
You mentioned an 82C thermo.
The original spec. for you car is an 87C.
That is start to open spec.
This may attribute to your temp change more than the a/f ratio difference.