It takes a LOT to get 44s moving, especially in mud! Even with the 5.13 gears, that's a lot of weight. The Performer 390 is only good for low end performance and low speed torque, so it should perform ok down low (where you say you're having a lack of power) but it would give up quickly. Really not a good intake for any kind of performance engine. Even with the gasket matching, the runners are very small. Maybe you have another issue such as timing but I'm guessing it's just the combo of a mild cam, lots of weight and huge tires.