Worth considering: 1 AU equals 499 light-seconds, or about 8.32 light-minutes. Now, the Enterprise
didn't traverse the whole width of V'Ger's cloud -- judging from the graphic, it had an "apple-core" shape and the ship came in at the narrowest part at the equator, which looked from the schematic (sorry, can't find a good working link at the moment) to be about 1/5 of the total radius of the cloud. If the cloud were 82 AU in diameter, it would be 41 AU in radius, and thus the E would've had to traverse 8.2 AU = 4092 light-seconds = 68.2 light-minutes. It made the trip in about 5 minutes of screen time in the theatrical cut, so it would've had to be going nearly 14 times the speed of light relative to V'Ger
-- i.e. it would've had to be going at warp inside another warp field. (V'Ger's warp field had to encompass the entire cloud -- or actually be the cloud -- in order to carry it along at superluminal speeds.) Unless you assume we just saw a cut-down version of a sequence where they actually spent over an hour staring at the cloud going by (cue the wisecrack about "as opposed to just feeling like they did").
However, if the cloud was 2 AU in diameter, then the E only had to traverse 0.2 AU = 100 light-seconds = 1.67 light-minutes in about 4 minutes (since I think about a minute was trimmed from the cloud sequence in the director's cut), meaning it only had to be going at about 2/5 the speed of light. So it would've been at impulse relative to V'Ger, which makes more sense. Thus, I prefer the 2 AU interpretation. I see it as a correction of a math error in the original.