Re: Air fuel gauge
If you have time, you can pull the passenger side kickpanel out. Pull the ECM down from its bracket and open the cover. If the truck was custom tuned (Code59), it should have a small microchip in it. If its an off-the-shelf chip (ATR or Kennebell), it will be a large blue/brown plastic chip. If it has a small black box cabled to it, its possibly and Ultimate.
If you have a laptop, you can download Datamaster, and buy/borrow a ALDL cable. The program scans the truck and lets you datalog to see what the truck is doing. Its very helpful in telling you what boost & timing you are running.