Hello all. New to the forum. Having a little problem with intake and exhaust....

I recently added a 40 series flowmaster dualed out to 3", and a K&N CAI to my 2003 4.7. Truck hasn't been as fast since. It's more noticable in the lower RPM ranges, expecially at highway speeds. I unhooked the battery for about 20 min to drain the system, but truck still doesn't have as much power as it did when it with stock intake and exhaust. Someone please help. I always thought, bolt it on, go faster!! Is there anything i am forgetting to do?? I have talked to flowmaster tech support, but they dont have a clue as to what could be wrong. Did find out that the muffler guy stuckthe cheapest40 series on there that was designed about 15 years ago. Flowmaster said that wouldn't have anything to do with it though....
When i go down the highway in 5th gear, and puch it, just get alot of exhaust noise, and hardly any acceleration. Sounds like air/fuel mix is off, but dont know how that could be possible.