I was looking at mufflers and came across the Dynomax Ultra-Flow SS mufflers. I keep hearing how glasspack (cherry bomb) mufflers don't flow well at all. To me these Dynomax mufflers have the same basic strait though design. Just wondering what would be different and make them flow so much better? Whats your opinion on these?

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It's the expansion chamber that influences the pressure drop. Glass packs have a tiny expansion chamber.

A 2 1/2 inch glass pack usually is less than 2" in diameter inside with louvers. Many 2+ inch inlets are only 1 1/2 inside diameter.

The muffler you show is straight through the same diameter ,or even larger, with holes in it, not louvers.

It also ain't very quiet either, Maynard.