I have a 1988 stock-ish zilla.  No porting only mod is a 13:1 o-ringed head running on race gas.  It had a dyno port mid-top pipe on it when I bought it.  I didn't think it ran very well with that pipe.  I had an FMF laying around so I put that on.  I am super impressed with all the bottom end torque this pipe makes.  It seems to pull the front wheels effortlessly from what seems like idle.  Since I ride this one in the trails, it is a great pipe for that.  I have a HPR zilla with the HPR 19 pipe on it and thought about trying it out on this stocker.  I do not want to loose ANY of the awesome bottom end torque that this FMF puts out.  I know that I will gain lots of top end HP with the HPR pipe.  I can't seem to come up with a dyno chart for the FMF pipe on a stock zilla.  I found one for the HPR pipe on a stocker.  Any input would be appreciated.  Or if someone has a dyno chart of a FMF pipe on a stock zilla.   Thanks. 

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?