Yes, the voltage values seemed to rise when the throttle is opened as expected...Although I did notice that when I let go of the throttle, the value jumped pretty high, then settled back to where it should be...not sure if that's normal or not.

Also, I'm quite sure the head gasket is fine...since I have had LOTS of BHG experience with my 3rd Gen Toyota Supra turbo...which also has an inline 6 and blows head gaskets pretty much constantly LOL. This car shows absolutely no signs of a blown head gasket...and I've smelled coolant being burned before, this car is making a different smell entirely, I'm assuming it's unburned fuel. Plus, coolant won't foul plugs...in fact, it usually steam cleans the cylinder it's been leaking into...so I'm pretty sure that isn't the problem.

The CEL is still lit tho, which means there HAS to be a problem with the Air Mass Meter...unless the ECU is really the culprit, but I'm assuming that they don't go bad too often?

Does the manual say anything else at all about the Air meter? Thanks!

edit: I should also add that I was looking at the old plugs I pulled out of the motor earlier, and they look like they have a hard grey coating on them that I can chip off with my fingernail...only on one side of the electrode...the other side is much cleaner...they are all like this. I'm guessing this is carbon fouling?

I have also noticed that after just 300 miles of driving, the car is starting to become progressively more difficult to start. I'm guessing this means that the plugs are starting to foul?

Doesn't sound like it to me. Could it be oil fouling because of valve stem seals? Look at these links and tell us which picture is closest to your plugs:

http://www.dansmc.com/Spark_Plugs/Spark_Plugs_catalog.html

http://www.centuryperformance.com/spark2.asp

__________________
"It's not about how fast you can go, but how well you can go fast."

Bob in Richmond

'97 S320 (LWB), Ruby Red Metallic, 73k miles
'97 S420V, Smoke Silver Metallic, 155k miles

Well, no other stuff in the manual about the air valve sensor. It's just a simple Potentiometer apparantly.
Not actually having checked one myself, I can offer little help about how it affects the engine controls.However, with the motor idling, if I push the air valve gently down and hold it down, say, one millimeter or so, it will stumble, then recover and smooth out.
What is happening is the air valve controls the fuel delivery thru the fuel distributor; when you push down you increase the fuel, then the EHA compensates and reduces the fuel. But don't know how the air valve sensor data plays into the computer reactions. I assume it's similar to a GM throttle position sensor, where the timing and fuel enrichment are controlled in relation to the throttle opening.
- OK, not a head gasket. And apparantly not the air valve sensor.
Let's think some more.
- These engines can dirty up plugs in a hurry, particularly if the valve sterm seals are leaky. But 300 miles is a bit extreme. I see that type of buildup beginning after approx 2000 miles, but I have really good stem seals and 1/2 quart oil usage in 5k miles.

Maybe, it's running really rich; smoking, fouling plugs, and the code 4 just happens to be what it set because it expects the air valve to be open more;
or code 4 was set because the German engineers think differently (Ha).
We (you & I) really don't have any info about why/when these codes set. So maybe it's not the fault of the air sensor?
Maybe the EHA valve is richening it up, and system is trying to react, but can't lean back down; so it stumbles, fouls the plugs, starts hard cause it is flooding slightly?

I guess if it was me, I would check that on/off ratio with the Sears meter, as I outlined above. That can check so many evils, such as the enrichment EHA valve, the O2 sensor, the fouling plugs, the entire fuel delivery system basically.
Also, check this out! There is a chart in the manual that outlines a series of probable faults, depending on what the ratio reads. If you check the ratio and report, we can possibly narrow it down.
Example: a constant 40% reading indicates a problem with, guess what, the air valve sensor. A constant 30% indicates faulty coolant sensor. etc, etc.

So, humor me, go buy that meter and plug it in!
I'll stay with you on this (at least until the antibiotics kick in and kill this cough, and I can play golf again!). Just kidding, I want to learn something about this, too.

DG