I think AEM has the best quality, but they dont have a CAI although it looks like a good design.
I have heard mixed opinions about Injen. Some swear by them and some say they wouldn't put anything Injen on their rides.
As far as MHP, they are a small company that charges a pretty high price for what they are selling. And most everyone has had problemswith the fit and finish. Basicly not fitting at all and having to mod the thing.
So I would go with the AEM Short Ram.