No cat or muffler
#2
I did a K&N and 3" downpipe to 4" pipe with no cat. It still had a muffler (you can reach your arm straight through it). I got about 1-1.5mpg better combined. Sounds really good, like a fedex truck. They all hear ya cummin from the end of the block. Smells better now too.
#3
I just put on my 4" SS exhaust from the turbo back with muffler and like the sound. I am sure that the milage will climb based on the power gains from the freed exhaust. Sure can feel it in the seat of the pants and even the sound of the turbo spool.
#4
My cat went MIA 3 or 4 years ago and have noticed a definite power gain from the freed exhaust as well as a 2 or 3 mpg increase depending on how heavy my right foot is. As to the sounds it is not all that much louder than before......mater of fact many of my friends that don't know what I've got under the hood say it sounds a whole lot like a fire truck going down the road. I hear a drone at highway speed but just turn up the stereo to compensate.
#5
I had 3" straight pipe on my truck, been a few years ago. Sounded really good but the drone at interstate speeds was really annoying. Picked up a 24valve silencer and all was good. Since then I've gone to a 4" turbo back with muffler and sounds great.
#7
Went with a free flowing muffler, much better and very little restriction.
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