Originally Posted by nitehawk
Hmm, what's the cell density of the stock secondary cats?
Dont have exact cell count but it is high.
I wasnt able to see anything when looking through stock mid cat.
Reason why I initially installed these hfc together with catless downpipe is because giac told me that i would notice about 20-30 hp difference with their tune if i have stock secondary cats vs not having them at all or replace with hfc.