Downpipes don't have O2 simulators. You normally have to buy them separate.Originally Posted by GReddySetGO
Luckily, there are a few options:
1) Buy a $50 get-rid-of-your-CEL box
2) Buy some anti-foul bung things and hope they work
3) DIY: http://www.vfaq.com/mods/O2bypass.html
Old knowledge is good.