I don't have a lot of experience with TiVo stuff, but you might see if you can add the file in NeroVision Express 3. It is a video editing and DVD making utility that can change the quality settings. Look under the MORE button to set the Video preferences.
If you don't want to make a DVD, there is an option to export the file to some other format, and the settings will be on the configure button on the export page.
I don't believe Nero Burning ROM has the capabilty to change the quality settings, it just burns the files. I don't know what Nero Recode will do, since I have never used it.
It sounds like the file is not a very high quality recording. I don't know if you can change that in the TiVo, so the final quality won't be much better than the original. You might just think about putting several on the same DVD and leave the quality settings as they are.