I think it's bs! 50 hp no way. Maybe 7hp. The f90 secondary cats flow is not as restricted as some. I was reading a different thread with a flow bench test. Quoted from post:
F90 Factory second cat flows 542cfm at 28 H20
For reference an open 2.5" pipe flows 515cfm
An open 3" pipe maxes my bench at 702cfm
2017 Z06 secondary @ 482cfm
He said the Z06 gained 35 horse, 18 at the wheels by deleting ALL 4 cats! He said in comparison the F90 on a 3" secondary 21hp at the crank. We are just talking secondary, not all 4 cats. 50 hp lol! Maybe 4whp. The F90 secondary cats are tiny compared to the Z06's.
https://f90.bimmerpost.com/forums/sh....php?t=1551285