The pac brake cannot void your warranty unles it is proven to have been the cause of a problem. The jacobs brake is what chrysler sells & warranties. Too much back pressure could float a valve. Pacs back pressure is set to 60 lbs as is jacobs.
I'm having the Pac brake pxrb installed tuesday. I didn't like the idiea of the vaccum pump or the longer serpentine belt on the jacobs. If the air compressor goes bad it's cheaper to replace plus you have onboard air to run other things like air horns, air bags, or fill tires if you put a big enough tank on.