I did the same on my T/A hood scoop. There is very minimal HP gain. However there is something to be said for the notion of "
why have a hood scoop if it isnt working"?
I chose to open it up b/c when I finish the engine build I am going to plumb the scoop directly into the intake port. The kit that opens up the T/A has new perforated front grilles that replace the factory solid grilles. By themselves the perforated grilles will NOT supply enough airflow to allow a direct port, although its plenty to port into the CAI and keep the warmer (i.e., less efficient) underhood air away from the CAI on a factory set up, since the CAI also allows additional air from other angles.
On my set up I plan on either fabricating some butterfly valves and throttle linkages or customizing from an SMS hood and blending those into the port and starboard sides of the hood scoop itself. That way I will run the grille supplied airflow under moderate throttle and when I open it up (1/2 throttle thru WOT), the butterfly valves will kick in adding more airflow into airstream. Plus the butterfly valves in operation look friggin awesome
Here is a really good thread on the basic T/A hood kit. Posts 10-14 talk about the coolant reservoir issue - some need it - some dont.
http://www.challengerforumz.com/showthread.php?t=100885
Good luck with this - if you need help on the install PM me and I can walk you through it - Andres