I currently have a stock muffler, single in/single out. I have installed an AFE CAI, but want to increase flow in and out, so I am going to have a FlowMaster 50 installed. I am looking at going back with the stock set up, single in/single out. Is there a benefit to having a single in/dual out set up. Does it matter or is it a looks thing? If single in/dual out will increase the air flow, generate more HP, and provide oppotunities for mpg to go up, then I will do it, but if single in/single out performs the same way as the dual out, then I will stick with that.
The dual outs is mainly a looks thing. As long as the single pipe can flow enough it will perform just as well(and our rams have 3" diameter exhaust pipe that flows enough), so you wouldn't benefit from dual out. I highly recommend though that you go with a straight through type muffler(magnaflow, dynomax, others....) instead of flowmaster, as flowmaster is baffled/chambered and does not do much for performance. If you want to go a step further replace the stock y pipe also. The rest of the exhaust is pretty good unless you really go far with engine mods.
I plan on doing something similar with my truck, I am replacing the stock muffler with the 14" magnaflow muffler, and also will be replacing the stock y pipe.