Ted made a good point,and I was going to post on it earlier. If the truck is stock,your probably better off just turning the star wheel towards the engine to gain a bit more bottom end. If the AFC is slid too far forward,you get too much smoke,and have to adjust the star wheel way too much. I could see how this would affect fuel economy too.
I went through it all on my truck,when sliding the plate forward,and have ended up going back to the original AFC housing location,and turned the star wheel approx 30 clicks towards the engine. Same response,same bottom end,just a lot less smoke.