My new SEL makes some clicking noises too. Hard to tell if fuel injectors or valvetrain. Now if you want to hear some rattling that will make you wince, you should hear my 2000 Ford Explorer with 200,000+ miles 4.0 SOHC. When it starts, sounds like a metal chain is being dragged off the end of an aluminum table. But still gets close to 18mpg if i baby it.