You should replace the o-rings on the injectors when you replace the lines. The kit comes with all of the rings for an FI bike, but maybe they don't make it anymore. The individual ring numbers are 27237-95 for the top of the injector, and 27244-95 for a little lower on the injector (schematic calls this one the middle o-ring). Make sure that you lube them, and the o-rings on the lines, with a bit of oil after you get them on.