Thanks for showing that article........swapped out the Ultraflows for the Borla Pro XS(same design as the Ultraflow) on an 11:1, 550hp 440 with 3" X-pipe. The Borlas are a bit more expensive but a touch quieter and judging by the article, the best performing.

Overall construction is similar to the Dynomax, but side by side a bit higher quality in the Borla.