I finally got around to swapping the HPR 19 pipe on to the stock 88 zilla.  Compared to the FMF, it gained a TON of top end power.   But it definitely lost the snap and massive torque on the bottom end for woods riding.  It takes a lot longer for it to come up on the pipe where the FMF just always seems to be at the right rpm in the woods.   I had to know and now I have my answer.  Based on the dyno runs that I have seen, it seems that the HPR 19 makes the lowest RPM torque and horsepower of all the big high volume pipes.  Perhaps the DCS 7 will have more bottom end?