Take a look at throttle opening percentage / voltage at idle.

If the numbers are low, it points towards a vacuum leak post throttle body because the throttle is closing to maintain idle speed. A failing brake booster can cause a vacuum leak also.

If the throttle numbers are normal and MAF low, you have air entering between the MAF and throttle body ( maybe from the crank case breather through a oil cap / dipstick o ring ).

Great tip, I didn't think of that.

I replaced the TB to Elbow rubber seal and reset the mixture adaption. So far 90 miles with out the code coming back on, all monitors are ready except for the cat and evap, I've tried to complete the drive cycle twice.

The old seal was starting to get hard and would crack a bit when you bend it.

Hopefully I'm good to go. Thanks for the help.

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1999 SL500
2003 C32
2002 S55
2004 S430
2003 E320
2004 E500

After 300 miles the codes have came back on.

I noticed my intake manifold pressure sensor is reading 318 hpa at idle which I believe should be a negitive number, when the engine is reved the number doesn't drop below 200s. Maybe I'll try swapping pressure sensors. What is your IPS reading at idle?

For future search purposes my iPad scanner shows these codes as P0170 & P0173 where as my sds shows P0171 & p0174

Also to add to the parts replaced list is:
#6 OE maf rubber seal and TB rubber seal

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1999 SL500
2003 C32
2002 S55
2004 S430
2003 E320
2004 E500

I scanned the IPS on my E320, the readings are about the same but the E320 range for this sensor is less than 500 hpa vs my S55 shows the range should be less than 0. Kinda strange but o well. I think I'll have to buy a smoke machine now.

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1999 SL500
2003 C32
2002 S55
2004 S430
2003 E320
2004 E500

Smoke machine is pushing smoke out the egr vent. Is this normal when no vacuum is applied to the egr?

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1999 SL500
2003 C32
2002 S55
2004 S430
2003 E320
2004 E500

Fix that next. Wowzer, good picture.

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Jim

I put some duct tape over the 3 ports. The CEL went off after 3 short drives with all monitors set. A new EGR should be the final solution.

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1999 SL500
2003 C32
2002 S55
2004 S430
2003 E320
2004 E500