exhaust routing question?
 

I had a flowmaster 40 series muffler installed today dual 3 inch to a y pipe in and single 3 inch out, sounds awesome! was asked by my friend if it makes a difference that the factory had dual in and dual out to a y pipe for single pipe finish? i think im flowing more exhaust out with the flowmaster anyway. my buddy thinks its probally the same as stock because of the dual to y pipe in, and single out is different than the stock dual in and dual out to single? cant be true the stock muffler is a dinosaur!.. what do you guys think?

thanks in advance!!