So my old mani had the notorious crack right where the o2 bung is; so I replaced it with a DC header; little did I know that the donut gasket was a 2 in, and I needed a 2.5 gasket for my new downpipe. So I ordered a new donut; but until that gets here, I'm running open header. My question is does running open header make your MPG extremely horrible? Cause this **** is going through gas like V8 ever since I replaced it. I have my primary O2 hooked up and the car runs fine, no idle problems; just loss of torque for obvious reasons.

 

You're probably just flooring it more. I would.

 

OBD1 or OBD2?

 

Assuming it's a real DC Sports header, the bung is right there near the collector. without an exhaust attached to it, you're getting a lot of oxygen sweeping backwards over the O2 sensor, which is confusing your ECU, and making it run rich as a pig.

 

Ayy! lol probably all three honestly. I floor it more, and yeah there's no collector till I get that new donut and it is a real DC sport header and the o2 is right next to where the collector bolts up so yeah lol. It's an OBD2 in a 96 Sedan DX