:iagree :iagreesstockton said:definitely go the route of injectors. Even if you throw on another box, you won't notice a whole lot more without injectors, not too mention that is a lot of stress to put on the VP. Like others have said on this site, with stock injectors its like trying to get a watermelon through a straw. They are just too restrictive. With your set up, a set of RV injectors or nozzles will go a long ways for you. many people prefer nozzles because they cost less and you can get ones that are a lot bigger. You can get a 125hp nozzle for under $300 dollars and on your truck that will make a huge difference. I wouldn't recommend that for towing, but it's do-able. I'd look into a set of stage 3 or 4 jammer nozzles if I were you.
other than that, smarty, will stack, Blue chips FMS or Redline will stack. there are probably others out there they just aren't jumping to mind right now.