Hi, I see you've done quite a bit. My first thought is with the 160 stat. and the high volume pump and the under drive pulley, you are moving the water too fast and it is not staying in the radiator long enough to cool. I would start by putting in a 180 or 190 stat to slow down the water flow. The reason I believe you're running cool while moving is the extra airflow through the rad. Good Luck Let us know what you find out.