My drag downpipe does not have o2 bung and flange to the cat. How much should I expect to pay for the flange? for welding the o2 bung and the flange?
SHould I put a flex pipe at the end?

 

Look on ebay for flanges, or ask someone in the welding forum, that flange might be 5-10 bucks and i would reccomend putting a flex pipe because i didnt put one and welded my exhaust straight to my header and 2 months later i was raing and the welds blew off, the guy said its because the moror is pulling when reved, could have been his welds, lol hope i helped out