I tow avg 3-4 trailers per week from 10k-18k. Towed a 40ft bumper pull today 13.9k from Sidney NB to Dallas Tx... the wind was really bad. So, I started out about 4am and everything was fine.. ran into some wind then some more.. I'm usually able to tow around 70mph with no problems using cruise control.. I never really got much over 70 or did it stay there.. the boost was running 20 most of the time and the exhaust temp around 12 , if I tried to speed up after engaging some wind gush or going up in elavation the exhaust temp would go up but more importantly the coolant temp would spike about 3/4 on the guage. I could lock the trans in 5th and keep 60 -65 and the temps would go down. I have a 4 in exhaust, sb cold air, pusher intake, and head studs thats about it for eng mods.. EFI cal with tow loaded. Oh,, I used a boat load of fuel.. I personally believe that it was all because of the elevation and wind but wanted to get some input...

Oh,,, I have a speed steed manifold waiting on a 63 67 tater turbo.. which should be in by next week.