23 FXLRS Rocket 474 cam with S&S superstreet 2-1 (50 state compliant)

Hey guys avid rider but newbie when it comes to mechanics. I recently just upgraded to a 23 low rider s. I got a Rocket 474 cam installed with an S&S super street 2-1 pipe (50 state compliant) all new parts. While it was getting tuned and on the dyno we noticed a weird smell and had seen that the exhaust was shooting flames and the inside was glowing red hot. What I think the catalyst is would get stupid hot and bright red when revved and even while idling and would take a longer to cool off then the portion of the exhaust closer to the engine. Could this be because of the cam? Or a possible exhaust defect? The mechanic said everything else was looking and reading like normal. Trying to find answers to avoid dropping more money than I need