Everything I see says they are sold in sets of 2. Looking at the pics there are 4? Would you need 2 sets or is one order for $179 going to do it?
EDIT: I see, its just not the "nubs" that attach to the rear diffuser, its a whole new piece, one left and one right. Got it

Also for those that have them, how do they attach? Drill holes and screw them down? Double stick tape? etc?

Never knew about these.