Of these two which sound better(I know this is based on your personal opinion). I have not heard either on a 3.8 so i have no clue and am looking for your personal opinions. It would be connected at the Y to a 3.8, 5 spd.
welllll if u want a reallly deep muscley sound that sounds like a freaking 427ci engine go with MAC's. If u want something that is really raspy go with flows..... i personly dont like flows on v6 mustangs....... i had flows and it poped so bad i hated it..
This has been asked about a million times. Flowmasters are probably the loudest. I love mine. I happen to like the "popping" as wickky puts it. I have the 40 series and couldn't be happier (unless of course I had a v8). I don't believe in bashing other mufflers (like the MACs) because its really just a matter of opinion. Go to http://www.mustangexhaust.com and listen to the various mufflers for yourself.
In an ideal world, yes, finding others would be the best way, but in reality, most people will take you for a stalker if you try to follow them on the streets and pull them over.
Either scope them out in a parking lot, school grounds, or find a few clubs in your area.