Pretty sure I need new cats for the pre-LCI 98 740iL. Going to do a backpressure test to confirm once the the new waterpump is in.


anyone have pictures of how aftermarkets like the Dynaflow installed? The header collects to a single pipe per side and then comes in at an angle. I have access to a lift and am comfortable welding- just not sure how to manage the curve without an exhaust pipe bend from the headers. Only exhaust work I’ve done is straight.


The other confusion is what cat to get, I’ve read everything from 2 to 2-1/4 to 2-1/2 for pipe size. I checked the pipe at 2-1/4 however it sounds like it might be 1,9” on the inside because it is double walled.


choices:
2-1/4x2-1/4 #53005
2-1/4x2-1/4 #94105
2-1/2x2-1/2 #??????


Thanks for the help!