New predator with 160 t-stat
only lower the temps on the highway. Fans w/o thermostat
will put you to a more consistent coolant temp (194F) and
make you able to "tune tighter" - no stoplight ping on a
tune that's otherwise good, etc. The 160 'stat will put you
about 177F instead of 194, if you set the fans to support
it (most advice seems to turn the fans on above the crack
point, in which case you will have wider swings but operate
generally at a higher temp.
I saw a 1MPG city hit at most from a combination of cooler
'stat and converter. It's a nit as far as I'm concerned. Also
got little difference in maximum no-KR timing or minimum
no-KR power enrichment (Predator) out of the 'stat, but
this was with well-managed fans.
I would say set the fans, leave the 'stat in the box and
tune it up as best you can for a consistent 194F coolant
temp.

