We went thru a pi--ing contest here - a DA50 vs a ZDZ50- on pipes
Not my idea but I watched anyway -
when it was all over and the smoke cleared - performance on any given prop and pipe combo was about the same --on the bench
on 22x8 Mejzlic - 7500+ was normal
I setup a ZDZ50 3 years ago on ame setup (actually using the AMT pipe and the results were excellent--as long as you stayed on the 22x8 prop
shifting to 24x8 -
new ballgame - on either engine you MUST increase header till rpms on the ground are in mid 6000 range or performance is a flop - grumbling , dead spots top end going lean -on and on.

I see veeeery few tuned pipe setups which really boost power --and do NOT cause a lousy midrange peformance

Maybe my standards for performance are different than others

in early 90's we piped .60 OS engines for 15000- ground and 20000 in the air
huge power -shi--y performance when it was all said n done. nothing smooth about it
The guys who are happy with their setups typically match prop and pipe and get secent boost and workable midrange
Frankly I don't think anyone has a "secret"or perfect" pipe for any engine -- just a pipe that works in certain pipe/prop combos
My 80 ZDZpipe setup was very unimpressive on first runs - I had a undersized prop load and ran at rpms above best tuning - switching to larger props I found the combo that matched -never touched the pipe or header .
I have had yahoos claim my results are "impossible " because they can't do it (actually never even tried).
My point is decide what power rpm band you want to run in - buy any pipe of large enough size -then experiment till you find right prop combo.