Fouraquest

Hey MP4...sorry again for the late reply, I've sucked at checking the forums recently.

Regarding misfire, I'm convinced there's still an exhaust leak somewhere. I've had some repairs done already but it still clearly sounds like there's a leak left. I actually had all the coils, plugs, and electrical connectors for the coils replaced late last year when I replaced the steering rack. I'm praying the leak isn't at the manifold studs, because that would be super expensive to replace, even though I've wanted to put new high flow manifolds on anyway.

All the PCV tubes/hoses are also new as is the PCV itself, so I can rule that out as an issue. I'm sure there's a vacuum leak somewhere, although I can't hear one and I've checked most of the vacuum lines a few times.

I'll definitely unclog those drains ASAP and check the ECU connections. That's a great idea. I'll report back as the solutions arise.

aTOMic

Are there even any high flow manifolds still available for these cars?

the green amigo

I would check your HPFP's, could be on the way out. Also have you replaced your injectors or had them bench tested? Lastly these ecus like to die with a little bit water.

Fouraquest

So I figured it out. My ECU's are fine, so is the compression and the injectors. Unfortunately I have a leak at the passenger side exhaust manifold. It's pretty obvious given the symptoms, including a clear exhaust leak sound and the smell on the passenger side. Sigh. Going to be a big job.

MP4.2+6.0

FWIW, be sure it is in the manifold area itself. Reason I mention is the flex joints in the exhaust (further back) are a known fail point, particularly on the early 4.2's. I don't know the S8 layout, but have them x 4 on my prior D3 W12. Those can be relatively cheap where once out of warranty many owners with the issue have just taken it to an exhaust shop and had generic ones welded in.

Fouraquest

I've been underneath the car on a lift while it's running, and I've had all the flex pipes replaced recently. It's 100% the manifold.

Bigdriver

They should both track virtually identically.

Fouraquest

I’m not sure what you mean here