So it sounds like there are a few deterents on increasing power output on the E53 3.0, but no one has really tried? Surprising to me since the BMW inline 6's of this era are pretty impressive, which I can't say the same for the V8's they made which ESS and dinan made supercharge kits for.

Upgrading the trans cooler will solve the overheating issue, which is fine, but anyone who has towed the max rated load with the 3.0 probably can share my experience with it needing a bit more power.