The first thing I'd do is to check for vacuum leaks. If you have a vacuum gauge or can borrow one, check the engine vacuum at a port downstream of the throttle body. If the gauge needle is not steady, then you have a leak. Look for a hose that isn't connected or a port that doesn't have a hose or cap on it. If all that checks out okay, then very carefully spray a chlorinated spray, like throttle body cleaner, around the points where the intake manifold meets the cylinder heads. If you hear the engine rev up you have located a vacuum leak. A couple of simple things to check before you start throwing parts at it. PS - if you purchased a used '07 intake, it could be warped, cracked, or the intake ports don't match the ports in the head. I'm not a HEMI expert but I believe there were some changes made around 2003.
