Exhuast vs economy

[mmandley]

I am wondering what to expect here.

I have my programmer on the way to PHP right now to get switched to a Diesel set up and then get my tunes uploaded to it.

My question is, i just got my 4inch MBRP straight pipe exhaust delivered. If i install this now will i see anything bad happen to the truck?

I was told no issues will arise as the truck prefers an open exhaust but then i also hear without the PHP tune i will lose mileage on my MPG.

Can anyone answer this? I am planning on a 1500 mile trip in a couple weeks and really want to install my exhaust but don't want to sacrifice my mileage on the highway.