Jason,
You should be fine, 165 cant hurt it. I suggest running it at 160-175 after a 5-7 minute run. Yes it is normal to lose punch, partly due to heat, but mostly due to voltage drop in the battery. However you may want to get better acquainted with your slipper clutch since switching to our motors. You have way more punch now than before, and traction control is huge in offroad.
Bis,
Aint seen you in a while man, starting to have withdrawals. See you at Hot Rod on the 24th.
The MurfDogg