I personnally have a set as trial peice,I dont have a dyno but have tried these pipes on four diffrent motors i have built in the past two months.all motors were ported and carbed.I have liked the way the pipe signs in and how early it signs in,you will have no prob trail riding or dragging .My advise is get them chrome rite away I wish i did.The overall design of the expansion chamber works if you ask me its the smoothest transition i have seen yet.With these pipes ,stock carbs ,stock modded trans,4mil,ported,my boys bike ran a 5.0 in the 300ft with realtors.They work