Cheap Upgrades?
 

Alright guys I've been driving my company truck around for a little while now (08 6.4 F550)and want to upgrade it. Problem is that because it's a company truck I can't do anything extreme to it and it would be on my own dime. So what are some SUPER CHEAP or FREE upgrades you've done to the motor to help it out in the power department? Any opinions would be great but I'm not too interested in fuel additives, synthetic oil or anything like that. Thanks in advance.

I put a AFE PRO DRY S reuseable air-filter & it only cost me $57