Seems to me that you are assuming that you need that valve when perhaps that's not really necessary? SW is required for some model year applications (not ALL btw) but if all you want is for a dealer to do just what you want, then you need to call their service department for an estimate if out of warranty or you're just willing to pay for it anyway. If it's still under warranty and you have a real "diagnoseable" problem (check engine light, rough running, hard starting, etc), they shouldn't charge you anything but if you're requesting parts that may not be causing a real problem, they won't just do it under warranty just because you want them too. VCNA doesn't allow dealers to do that or everyone would. There is no recall or campaign that requires older parts be automatically replaced even if a newer PN has been made later in production.

If your 'evap purge valve' was bad, you'ld definately get a 'check engine' light before you'ld ever notice a problem with it, actually you'll never see that valve cause a drivibilty or gas mileage problem, just a check engine light.