The size, length, and shape of the pipe joining the chamber to the end can, all have a bearing on the characteristics of the power output.
A very small change to just one of the pipes on TYGA's GP style chambers in the area you are talking about made the difference between the pipe working just "OK" and working extremely well!
If you have access to a dyno then it would be interesting to see the effects of your trials!
Andy.
NSR-WORLD.COM