A long followup to Glenn's questions about setting up his A/F gauge.

I was curious how the CIS guys set their correct mixture. I've read the Bentley and the Bosch Fuel Injection manual and I understand how everything works, but I'm looking for how to set the ratio for a car that will spend most of its time running hard and revving high.

I've checked the voltage at the o2 sensor, and it bounces b/t .3 and .7, but stays mostly b/t .4 and .68 it seems - this is at an idle of 900-1000. To me, this seems very good. Problem is, i've messed with the mixture screw a few times, and when I rev the engine or hold it at around 4000, I get a voltage of .2 to .3. This tells me I'm running lean on the top end. I don't have the FTE switch engaged so I don't know how this would compensate yet. Since the o2 sensor voltage when connected isn't accurate b/c the ECU reads it and adjusts it, hiding an overly rich or lean condition - right?

If I disconnect the o2 sensor from the ECU and reads it voltage while the engine is running, will that tell me accurately if the engine is running rich or lean (higher voltage = rich, lower = lean)?

The Bosch FI manual says I can also check the duty cycle by tapping into the frequency valve. I tried this yesterday and didn't get any signal. There is a red wire and a brown w/ blue wire. I've got a good ground. Am I doing this correctly? There isn't detailed instructions for checking the duty cycle in the Bently or Bosch. From what I understand it should be around 45-50%.

Finally, how does the EGT play into all of this. I see about 1100F at idle and over 1200F at around 2k RPM. This sounds high to me. I've heard around 750F is good for idle. Any guidelines for this number?

Does turning the mixture screw a 1/4 or 1/2 turn at a time a good way to do it, is there a base setting I can set it at to start with?

Thanks for any help,
PJ


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83 Rabbit GTI - future ITB