Any body ever tried a higher volume fan for the blower motor in the HVAC box? Soaring eagle offers a fan/motor combo that they say will move 50 to 100% more volume. Have a 2004 kenworth that I spent a decent amount of time rebuilding the HVAC box in the engine bay and the air flow at the vents is still pretty meager. I looked a bit for leaks in the ducting inside the dash (I am sure there are some but nothing I could find without pulling the dash apart.)
I know of one Soaring that was installed--was told the air flow only increased about 15%. The biggest issue I've found is heater core and {**** I'm having a senior moment can't remember the A/C part I'll call it a denser core} is plugged with dirt. Those didn't have much of a cab filter and would plug in no time. But the way the system was built from the beginning it wasn't real high output. The only fans I know of are oem.