Ok, well I am not running the CNG at all, its all gasoline right now. Here is a fun video
http://www.youtube.com/watch?v=zl5NlEZQqag
But your engine is not set up for gasoline. Look at pictures of a stock engine and observe what has been modified on yours. It is not exactly inconsequential stuff.
Example...you have an EGR code. Find the EGR tube and take a picture of it. Find the plastic DPFE sensor and take a picture of it. Where are they? The DFPE definitely isn't there.
Another example: you're asking what that vac line goes to...well, see that big round things it's sitting by? I and most of the rest of us in the US have no idea what the christ that is. It's slightly detrimental to us understanding it's function.
There may well be some people here who can help you better. But from my POV as someone very familiar with both your (stock) truck and gas engine peformance in general...I can still say that I'm clueless here.
Why is an unused CNG setup there in the first place? What equipment is on the truck that can't be seen in the engine bay? Also...post pics of the entire engine bay, por favor.