What's the prognosis on this plastic guard that covers the brake and fuel lines along the side of underbody? I read somewhere on here that it collects dirt and salt and could speed up the corrosion of the lines.

Leave in on or take it off?

 

Id keep it on, it will protect the lines from stones or debris your front tire may kick up since the lines there run all the way to the outside of the underbody. It has slots cut in it to let water drip out anyway.. i guess you can argue either way if it helps or hurts, but you can always remove it once in awhile and clean out any gunk. I replaced all of my 5 lines (3 fuel/2 brake) and i still put my shield back on

 

I'm a believer in keeping the shield on.