If you already have all that, you would not gain any more mpg. It's called "diminishing returns".
The first degree gives you the most, the second less, and so on.
Besides, it sets a code around 3 degrees, because it gets out of sync with the cam sensor. Now you could take the Rokktech and put it on the camshaft, with silicone sealant to keep the oil in. The rokktech on the cam would let you advance the crankshaft an extra 3-4 degrees (one degree of cam is 2 of crankshaft), and so you could advance it to 6 degrees without a code, but it would be too much at idle, in cold weather. ( you need to advance both the crank and cam, not just the cam, don't get me wrong, so I am assuming you would use the tone ring mod on the crank).
The reason for no rattle w/Smarty is probably because they don't start advancing until it warms up.
You already have a 2wd, so I'm assuming you're getting about 23-24 mpg? Free wheeling hubs (for a 4x4), and a bedcover are the other two mods that would each give about 1 mpg. And get rid of the bugshield if you have one.