How much do HJS cats flow compared to a straight pipe?

Show us the data! Without flow data it’s impossible to make a valid claim. As always we suggest looking at all claims critically and not taking any percentage claims without solid evidence as proof of performance. HJS cats DO offer industry leading flow without triggering a check engine light due to the high amount of precious metals that perform the job of catalyzation. HJS claims a 60% reduction in exhaust back pressure here.