I don't care what the rating is
 

It's what you can do with what you have . As 10 sec Dodge say's . The Challenger is a heavy car. It runs good and handles good on the street with the 5.7 . And the SRT 8 is even better . From what have been told . I haven't driven one. Power steering and all sort of stuff rob power from the engine . Under drive pulley's can help some . Or take the power steering off as I did on my 71 Buick GS 455 Stage 1 and put a manual box on . And the air conditioning . I don't plan to do that and dont think many other's would . But it does add HP back to the car. I priced the Magna Flow exhaust for my 6 spd yesterday . The best pipes and everything . Was $1500.00 at my friends muffler shop. 10 sec. Dodge is that what you have on your's . And what brand header ? I can handle a little more rumble after getting used to the stock exhaust . I think 10 sec. Dodge has shown what the Challenger can do with minor mod's. Good Job.

Remember the cross Ram's
 

The longer the tube from the intake valve . The more ram effect and more fuel and air into the cylinder . Also a cooler charge with being away from the engine heat . A sort of tunnel ram sideway's.

In English to the above, it is the intake/exhaust space that makes the differnce. There has always been a difference between the truck and car raitings on the Hemi, take the Charger and Ram as examples, due to underhood space restrictions.

Exactly what I was getting at KYChallenger and Axle with my example but you both were more concise... :)