Very odd! I have an 03 6.0L 4x4 and the performance was just the opposite for me. I have been happy with it. Mine is just the module, no attitude and only 3 settings, 50, 75, and 100hp gains. My mileage stayed the same at 13mpg.
Is yours a module like mine that mounts under the hood. I don't think it is even possible but did you plug in the wrong harness. You pull the middle harness of the three from the pcm and plug it into the module's empty slot, then the edge pcm harness goes in the middle where the stock used to be. It should be that simple. Like I said, I don't have the attitude so that is all I can offer other than giving you their phone #.
(801)476-3343. I know they will gladly take it and have it back within a week. They will actually hook it up to that vehicle and test how it runs. They will also go through the whole board and make sure all is up to specs. I know everyone has their own opinion on what performance chip is the best so I am sure you will have people slam it on this forum so be prepared for that. I hope you get it figured out.
I'm about to slam those sulastic rubber springs I just mounted while I'm on the subject of slamming. It was a major pain to install them with just jacks and stands in the drive, especially if you have big hands. I believe I have to agree with a fellow that posted his comments about them in the suspension forum. "I literally had to strain to notice a difference if there was one at all". I bought them because I had a 2 level back fusion and heard they smooth and take the harshness out of the 3/4 ton ride. My back can literally notice a 2 lb difference in my tire pressure, but not these. If I didn't put them on myself, I wouldn't have known anything had been done to the suspension, no kidding.
As much of a hassle as it was on my back to mount them, I will most likely keep them on just to avoid all the BS I went through mounting them. I may just eat the $340. As for all of the benefits they claim like shorter brake distance, better handling, reduction in vibration, etc...I noticed none of those things.
So in my opinion, they did nothing for me, I may just take them off anyway and send them back to get a better riding shock all the way around as that will cost about the same and that WOULD make a noticeable difference. I am sure the Ranchos that came with the FX4 package are not the greatest.