throtle body has nothing to do with the ratling. its servied or cleaned because it has carbon deposits which makes the cars engine to breath not properly.
its only needed if ur cars vibrating a little or having issue achiviing high revs.
im sure 2005+ cars are better then mine ive got a 2002 since last four years. the only thing i did was changed its brake pads in august 2008 and added a new battry in January 2010. have covered aprox 40+ miles in Karachi, came 51k miles and now its around 93,000kms
PS: if u wanna get rid of ratiling u shud use once in every 3 refills, a 10 liters of Hi-octane and 20 liters of super fuel in every refill worth 30 liters