The mustang dyno is a heart breaker if your looking for numbers alone. The best I ever had on a mustang is 407 RWHP which equals 456 RWHP on a dyno com. The mustang is a great tuning tool though.
Thursday at the tuning school, we did a 2011 E-force grand sport C6. He had the 3 inch pully, LG cam, bolt ons, meth, 64 # injectors and was about 600 RWHP on the mustang dyno. Its was really impressive.
the manifold looks stock on the engine, and you only hear a little blow off.