I ran the bills pipe  for about a year or two.  Bills was one of the first manufacturers to come out with a pipe for the zilla.  I did not like it.  It was marginally better than stock--but just...  Was a low end grunt pipe.  I had a paul turner I liked a little better than the bills than I have run a CT pipe for about 20 years. CT was by far the best of those two.  I just bought a Qv2 but have not run it yet  (rebuild/Restore project)