interestingly enough, the bentley breakdown of how the EGR works has some blurb about how the valve seat is cone shaped and has several cross sectional sizes - and the computer uses N18 to create pulsed vacuum to precisely control "all the different EGR positions for each cross sectional opening" or something to that effect. This would imply that it is not just an open or shut condition.
So - to see if this is possible from a mechanical standpoint, I used a vacuum pump to measure the vacuum and the amount of opening on the EGR valve.
NOTE: I give ranges because I know my guage will measure differences, I just don't know how absolutely accurate it is - the point is not the accuracy of the guage itself, just are there really different positions possible at different levels of vacuum?
1. It doesn't start moving until about 10" of mercury.
2. Then, at 11-12", the first part of the cone shaped seat is visible.
3. At 13-14", the cylindrical bottom section is still in the cone shaped seat
4. and at 15" the bottom of the top part of the valve is even with the top of the cone shaped seat.
5. anything above 15" just pulls the valve farther from the seat, until you hit 19" and the valve is fully retracted.
It looked to me like there were maybe 4-5 variations possible? Starting between 10-11" of mercury, and every inch of mercury until 15" the cone valve is restricting the cone shaped seat at a different point until it clears the seat completely between 15-16".
If anyone is *really* interested in this, I can take pictures of it as I do this (that would involve about "4 cans" - see footnote about # of cans per experiment).
regardless of what this might indicate, I am with wkendrvr and gofaster - have someone watch it as it is stock, then set it to 33768 and see the difference. Something fun would be to set it to the lower limit of 31768 and watch it there too.
Footnote: this was a "2 can experiment" meaning it took me 2 cans of beer to complete.