They are a good general pipe. They give good power through out the rpm range.
CPI's, Shearer's, Rocktes, Sniper's, are drag pipes. Their power deilvery is geared twards top end. Some come on sooner and pull a little better down low. Others build a few hp up top. CPI's are a popular choice for high speed general riding due to the fact that they come on sooner and pull pretty good from the midrange to top end. Shearers suposedly have a harder hit higher up in the rpms, and make a few hp over the CPI's. With a 2 stroke your always exchanging something to gain something. You want bottom end it is going to cost you top end and vise versa.
CPI's have been compaired to Toomey T5's on sterroids.
I run CPI's because they are hard pulling top end pipe that still maintains a desent midrange.