You will need some ear plugs!
My brother had a Turdbo Diesel that had straight pipes and I couldn't even carry on a conversation with him at a normal decibel level. I think that I am going to have the muffler on it and that way the safety inspection is still valid.
By the way, I got an answer from the manufacturer on my questions. Here is what they said.
"In answer to your question, the muffler is designed to be installed
either direction. There are a majority of the flutes that face one direction and a fewer amount that face the other. If you want it quieter, face the greatest number of flutes forward; if you want it louder, face the fewest number of flutes forward."
They also said this,"On your vehicle, you should gain about 16 rear-wheel horespower, approximately 35 ft/lbs of torque and your EGT's should be reduced by nearly 200 F." Is that what everyone else seemed to get with their changes?