intake and exhaust

[ticopowell]

Hey all again,
So I am thinking of modding the intake and exhaust first in my truck, I like the zoodad mod, and I am looking for info on what filter and possible intake modifications I should do. I mainly want towing power and gas mileage, and as much of both as possible .
The other question is what exhaust should I do? I have read about a few options, larger everything, straight pipes, stacks going up through the bed, which of these would be the most benefitial for what I want?
I have seen the phrase "down pipe" is that basically the first piece of the exhaust after the turbo that goes down to the muffler? and what are up-pipes? those go to and from the intercooler?
Again thanks for the help!