Can Mp3tag remove or modify LAME tags?

I just used Mp3tag to remove all the tags (ID3v1, ID3v2, APE) from a set of mp3 files, but dbpoweramp still indicates a track gain value contained within the file. It looks like the files were encoded using LAME 3.97, so I believe that they must contain a LAME header. Can mp3tag either modify values within the LAME tag or else remove it completely?

No, Mp3tag won't.

Does the LAME Header's track RG bother you? Most applications can be set to ignore it (or won't even decode that one).

If you really need to remove the LAME tags (which I don't recommend, in general), Will's WAP VBRFix can do that (plus some other stuff).