I have a 2002 saleen s281. Is the stock air intake that comes with the car a upgraded Saleen intake or is it the stock ford intake? Is it worth upgrading to a K&N or something else or is (if upgraded Saleen) just as good? Also, when I idle I will hear a rattle sound sound that will come and go. Only when idleing for a couple minutes. The garage said best bet is the intercooler to the supercharger has a small fan and that it is loose or lagging? Any ideas?