When you say exact same pipe between a Polaris and a skidoo it has me curious. You aren't trying to use the same pipe on two different brands I wouldn't think.
Either way, a tuned pipes final tuning is in the stinger. It is based on length into the expansion chamber and overall diameter. There were old pipe sets that had adjustable stingers that the end user could fine tune for altitude or temp or fuel or whatever.
When the pipes are made they come tuned. Tuned for a specific make and model. Any change to the stinger length changes the tuning.
With any exhaust, the idea is to get the hot gasses out as fast as possible while retaining the appropriate back pressure. The long stinger probably creates excessive pressure.
I'll end this with, I think
