Oh the list for me to get the right towing setup was very long… but I just pulled Siskiyou pass in 85 deg at 65 letting out of it. Scale weighed in:
Front 4750
Drive 7450
Trailer 17550
I honestly fought with temps the most but for sure upgrading to L5P oil cooler and aux cooler made a difference for the long steep pulls. My setup goes way beyond mouthpiece and down pipes though.
Come to think of it, I added a power steering cooler to help with brake fade which is completely gone now and that gives me confidence in the downhill but turbo braking does 95% of it.