Hey guys, I know there's a ton of older threads on this, and i'm not one to beat a dead horse, but I just thought i'd give my observations on mpg before and after removal of the hydrocarbon emissions filter.
My truck has around a thousand miles on it, and prior to removing the emissions filter I had averaged about 17.6 mpg. I removed the filter and then for the rest of that tank (which was full when I removed the filter), I calculate about 19.27 mpg. Now I realize that this is a new truck, and some of this may in fact be the truck just breaking in. But i'm still leaning towards the filter removal, because the change came immediately at my next fill up. I have noticed a SLIGHT increase in performance, but nothing too write home about. Nevertheless, it is noticable.
Honestly, I don't care about any performance increase that may or may not be there; however, I can say without a doubt that I have seen an increase of almost 2 mpg since I removed the emissoins filter.