[The Champ]

Originally Posted by amcmike

-The straight-through mufflers with packing (flow piping doesn't do 180* turn) flow the best.
-Turbo mufflers where the exhaust has to 180* and back again, are less efficient.
-Chambered mufflers vary a lot by manufacturer design. They rarely, if ever work as well as straight through. But comparing to turbo-style some are occasionally marginally better, many often worse.

Jim and Tom Hand would dispute your claims. Per their extensive testing on Jim's '71 Le Mans 455 powered wagon, the Dynomax 17749 had one of the lowest backpressure ratings, the lowest sound level, the fastest speed in the 1/4 mile, and the 2nd quickest time of all the tested mufflers.

https://www.pontiacstreetperformance...p/exhaust.html