So I have a v6 and I want to add dual exhaust to it. I already have a new GT bumper, and it's already been painted to match my car, now the real work. I've decided I want a shop to mod the pipes to an H pipe. I'm trying to figure out what Flowmaster 40's I need for it and was told I need to fit the size of my IN/OUT for it. I was told I want nothing bigger than a 3", Flowmaster's website suggests Flowmaster 942043 40 Delta Flow Muffler - 2.00" Offset In / 2.00" Offset, what difference would it make if I got the 2.50"? I know someone selling theirs reasonably priced and the 2" are higher. Also with dual exhaust is it required to have 2 mufflers? Sorry if these are dumb question, I'm still learning 
Thank you for any information!
Thank you for any information!