Based on what you describe it sounds like you kind of answered your own question as to the poor gas mileage. With the exception of the dual exhaust - I have left my truck basically factory equipped - although I have toyed with the idea of modifying the cold air intake but I am not convinced it will provide any real difference in performance. Given the mods you have made it sounds like any motor will suffer from poor mileage - it doesn't sound like its necessarily the fault of the pentastar....You probably also don't have 35x12.5" tires on it. My Wrangler averages 13 MPG. I have 35s, steel bumper front and rear, winch, 2.5" lift, and a few other mods. Its neither good on gas milage or getting out of its own way. Around town it fine, its HWY miles or mountain driving its terrible. Also your Ram is a LOT more aero dynamic. The Wrangler is brick being forced through the air.