Let's try this again: DOHC exhaust

[trent]

The manifolds I'll obviously use from the S52. But I'll need an X pipe for the O2 sensor and I don't know of the OBD2 midsection has that.

Stick the O2 sensor in the port on the rear exhaust manifold. That way it is super close to the head, it only pulls one bank, but so what. If your engine is that far out of tune that the front bank isn't close to the rear bank, you have other more important issues than O2 sensor location itself.

[matt]

I have a single 2.5 all the way back with a cheap aftermarket cat (with flanges so I can replace it with a resnator later) and a magnaflow muffler. I plugged the O2 sensor holes in the OBD2 manifolds and added a bung after the merge. This will work better later when I add a turbo using the same 2.5in exhaust.

ORCA is a good reference, but damn do they go out of their way to make things hard.

[cheades]

I have gone through a couple of iterations of exhaust now, I am only about an hour south of the border if you want to come down and look at the way I did mine (I have my old 2.5" Dynomax system if you wanted to buy it).