Thanks man. Just trying to give him the same treatment that I would appreciate.

I spoke with the Mercedes tech earlier, he said he thought the car was running entirely too rich. I told him that shouldn't be an issue at all, since the AFR's (in open loop) are 12.5-11.9.... and while the car is simply driving around, the ECU seeks stoich (14.7).

I'm still standing by the suggestion that a sensor (TPS, CPS, etc) had a sudden immediate failure. The car was running great, then had an immediate, sudden misfire that has not gone away since the failure occurred. So, it's not a heat-sensitive issue. MB tech says fuel, but until he shows me a black spark plug, I'm not buying it.

I put him in contact with Buckhead, so hoping they can work together to glean the needed expertise.