[pgermond]

You have something going on other than an a 160 t-stat. Most likely air in the system. Drill an 1/8" hole in the flange of a 190 degree t-stat, This will allow some coolant to flow before the t-stat fully opens.

As was stated, FE's like to run around 190-200. I had a 160 on mine and it ran like $hit! Look into a SPAL slim line puller placed behind the radiator for really hot days and traffic.

Good luck.