Louvers should point away from the headers toward the exhaust outlet!!
I found out from the "King" of glass-packs (Lucien Donofrio) that if you point them toward the headers you will effectively reduce the flow of a 3.5" muffler to a 2.5" or less at high output??
I did it his way and the power increase was very noticeable as was the NOISE!!!
Coosawjack
