You cant get it perfect but you can get close. Remember that long head pipes create too much vacuum at high rpm. You need a mid and end pipe with a big diameter and short length. The big dia. allows volume to move quick at low rpm but also controls high rpm velocity because the big dia. flows slower than a small dia pipe. The short length lets exhaust out quickly before it has time to create too much vacuum at the exhaust valve.

There are many other ways to control exhaust but the above is the easiest way.

 

Would that explain why the stock DS head pipe works so well with those two relatively short head pipes joining into a pretty good sized "midpipe" and why my Topgun starts expanding in bore so early?

Ron