I boiled the Wahler thermostats (the one that came with the car, and the one that I installed in January) and concluded that I need a better method of boiling thermostats! However, both seemed to operate just about the same. While those were cooling down, I found the dealer thermostat I bought and installed it. It was getting late and I did not have time to boil it for comparison. Now the car runs at 90C on the interstate in 80F weather. So, it would seem that my problem is fixed, OR (pessimistic) that this thermostat opens too soon and I still have problems
For time time being I'm leaving things as they are.