I daily drive my truck and I take it to the track so hopefully I can give you some input. Like most have told you already, throttle body spacer is a waste of time and money. I would suggest start with the a custom tune first, that's where you will see the better gains and you will need it to see any real gains from anything you add to the truck. I don't have the pedal commander but I have the 9-drive which is like $100 and it works the same way as the pedal commander. I've had it for about a year with no issues. The next one would be your headers, clutch fan delete, lower temp thermostat, bigger throttle body. Depending on how much money you want to invest in all of this next would be a bigger cam, stall converter and possibly new gears. Gears and stall converter would be the things that will start putting your transmission to the test. I would leave the CAI for last if you really want one or if you find a used one for sale.