Please refer to the attached picture (Bank 2 MAF has been removed for clarity) from a '96 SL600. If this is the Air Valve that feeds air into the exhaust, what would be the effect on engine performance and, more specifically, O2 Sensor operation if the valve were to be stuck in the open position? Arguably, this would be a rare case as (I presume) the valve is normally closed and requires vacuum to open. But it could get stuck open, maybe.

The reason this is important is that in troubleshooting this problem…
http://www.peachparts.com/shopforum/showthread.php?t=204133
…the symptoms seem to suggest an overly lean exhaust out of Bank 2. Yet the engine must be burning the correct, or close, air-to-fuel mixture, because the engine runs awesome!

QUESTION: How does one test for proper Air Valve operation? More to the point, how does one remove the valve from the engine (my R129 Repair DVD is unavailable)?

Cheers,
Jeff

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'96 SL600 (105K) Triple Black - Mein über-Fräulein
'79 240D (292K) Yellow/Saddle - Mein Spielzeug
'01 ML430 (123K) Black/Saddle - Wife's Ride
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'73 450SL - RIP
'86 300E - RIP
'88 420SEL - SOLD
'94 S320 - SOLD