[PeteKz]

Both my WURs (an 033 and an 089) act much the same way. This behavior is the roughly the opposite of what you would expect the WUR to do. I have removed, disassembled, cleaned, reassembled, and checked pressures on them. They still act that way.

What cam are you using?

I've spoken to several other members who have observed the same behavior. I'm suspecting that the WURs just work this way, however, previously people weren't aware of it because they didn't have AFR/lambda meters installed.

I'm probably telling you what you already know, that a 12.4 AFR at idle is too rich. That corresponds to a CO% of 8% or more, which is way above the spec. But, if you lean out the AFR to 14.7 at idle, then it starts to run roughly at idle and cruising throttle. So you run it rich for good drivability.

I am considering doing what several other members have done, which consists of installing a manual fuel pressure regulator in the CP circuit and bypassing or removing the WUR. Then you can dial in your AFR for whatever your driving conditions. For highway cruising and gas mileage you can set it to 15.5 or so, and for power, you can set it to 12.6 or so. Turn it down for cold starts, and turn it back up when warm.

Anyway, let's see if Tony has an explanation. Tony, do you have an AFR meter in your car?