iTunes Plus - VBR or not?

I'm sorry, but I don't have any experience with variable bit rate. All of my songs are 128 kbps aac, including my iTunes Store songs. Well, actually, I just checked songs from my latest iTunes Purchase (5/10/2008), and a handful of them are 256 kbps -- I guess those were iTunes Plus. How do you make them appear VBR or not? I see one purchased song, from 4/1/2007, that's 303 kbps (perhaps that's why it sounds rather crappy!) and it says it was encoded with FAAC 1.24+, while the vast majority of my purchased songs don't tell me what encoded them. Hey, there's another one: 267 kbps, encoded with FAAC 1.24+, purchased 8/31/2005. I don't recall for certain, but I think it also sounds of questionable quality. Both of these come from +Rare Requests, Vol. 3+. I don't think these are "iTunes Plus."

If you look at your preferences > general > import settings > "'Import Using AAC Encoder'; 'Setting -> iTunes Plus -> Custom,'" you'll see that it gives you the option of checking "Use Variable Bit Rate Encoding (VBR)." Mine is already checked, so I guess that's the default (I haven't imported any music using iTunes 8). Perhaps the iTunes Store music isn't encoded using VBR. I don't know, because I haven't bought any music from the iTunes store in 11 months.

In my case (granted, I haven't attempted to import any songs), even when I select custom and click OK, when I click on the drop-down menu, "iTunes Plus" is still checked -- not "Custom."

It's a strange one... I only just noticed it too.

Purchased music shows up as 256 kbps, whereas music converted using the "iTunes Plus" setting shows as 256 kbps (VBR).

Wonder why...