i would get a better flowing muffler than a flowmaster imo, the flowmaster is probably one of the most popular aftermarket mufflers, but is almost one of the worst flowing, i would do a dynomax ultra flo if you want a good non ricey muffler, and actually the part about only flowing as much as your smallest point, this is only half true, many of the fastest race cars have stepped headers which start out a lets say 1 5/8 to 1 3/4 it helps out on the low end, and makes more up top, and many diesels benefit from a 5" exhaust, even though the downpipe is only 4" or smaller, so this is not always true, and can quite often be the reverse