I picked up a 06 1500 MC recently. I'm noticing when I fill the truck up at 1/2 tank i get about 12 gallons to full. Filling at just over 1/4 tank i'll get about 17 gallons to full. I pulled the build configuration and the sales code is NFUS; 34 gallon tank. What are the chances the tank has been swapped? I've never looked into it but is there a way to look and tell between the 24 and 34