Pypes now makes some like these too. The Dynomax patent expired on the Flow Directors and PYPES now uses them. Theirs also work pretty well.
When it comes to the Hemi style mufflers (not sure what makes that) sound good & even better over time.Would love to know how all of these different brands compare with the stock-sounding mufflers offered by some companies, such as Accurate. As an old guy, I still remember how nice the 340's sounded from the factory back in the day. As an aside, I have Dynomax Super Turbos on my built Sport 340. They're loud at cruising speed, but that may be because, as I said, I'm an old guy now.