[BossCER]

Dave,
I don't have chassis dyno results yet, but I'll let you know when I do.

I had my Spiral Turbo's modified a bit. First we cut them almost in half (now about half as long) Then completely hogged out the center plug. Next step was to take and stratigically bore holes all over center section of auger and pipe that auger fits into (my augers are like 3 15/16" to fit into a 4" pipe). The last step was to fit the 4" pipe with auger in it into a 5" pipe and pack w/ stainless steel packing, taper at the ends and weld into place. All of this was done in stainless.
I can say that I'm very happy w/ the result as far as the sound goes, but like I said, I don't yet have any performance results. I've got a couple of pics in my gallery if you've got any interest.
Good luck,

Chris