I'm running their filter on my Shelby GT500 and love the quality. Because of that (and doing some homework) I bought their CAI for my RAM. I just installed it yesterday (write-up coming soon) and the fitment was unbelievable. It fit perfectly in every way making the install super smooth. It did change the sound but mostly at WOT, it's way more aggressive due to the removal of the resonator.
Not sure about the fitment for the G4's but I'd give it a serious look.