I actually have the CD now, and in the notes it says "additional music on track 2, additional music and lyrics on tracks 7 and 9 by T. Salvador" in the most footnote-y way possible. So it sounds like those are tracks where he wrote some of the original music which was replaced, but they obviously couldn't erase the lyrics Wayne sung.
Anyway 4 of the songs (Terminator Oscillator, Accelerate, My Destruction and Otsego Placebo) are just Xer0 on vocals and they're pretty solid. It puts them in a good position if they want to carry on after Vol 2 comes out, but I'd hope they change the name if they do. I always wanted them to go back to calling themselves Wisconsin Death Trip, their original name.