Inlet at baffle = fully open Cowl bottom exit smaller..
Ground OAT = 30F Taxi Temp = 73F Climb Temp = 74F
3,000' OAT = 29F RPM = 2,900 Temp = 66F
Other measurements during flight = 71 to 66F.
I also added deflectors at the cowl inlet to try to get my CHTs up, and to cut down on air flow coming through th scat tubing (see photos on next page).
Bottom line: none of this helped or worked to improve anything.
Looking at photo #3, if I add a 6" heat muff of the same design to the exhaust from #3, I can feed the cowl air to that 6" muff, it will leave that muff and get fed into the inlet of the 8" muff, which will then go to the cabin. Essentially the 6" muff will act as a preheater for the air going through the 8" muff. Not an inexpensive solution, but In for a penny, in for a pound. I really don't have any options at this point. Nothing else is working. A VW just does not produce enough heat.