Funny I just went through this same inquiry with the same concerns, I researched and have not found any negative comments on this unit. good gains, nice sound and no hydro worries! Received mine a few days ago, plan on installing it on fri. Feel free to PM me to see how the install went, seems to be straight forward.
(the only reason I can think of why one the 57 is exemp and the 63 is not, are the changes made to accomadate the 2006 have not been tested or approved yet)

 

Don't worry to much bro, COP can give u a ticket for any reason they like... even your car 100% stock

 

install is easy, be careful drilling the hole for your temp sensor, coz my drill bit almost went through my manifold thing. o yea.. dont be stupid like me and my buddy, we used one of the stock hose clamps coz we were wondering where the 4th one for the air filter went...... lol

 

o yea, one more tip, run the big 1/4 hose underneath the new radiator hose, so it doesnt rub up against the stuff on the underside of the hood, i ended up having a pretty bad wear spot coz my hose kept rubbing up under the hood due to heat and movement of the big hose

 

Thanks Ill keep it in mind!