The 2000+* use shocks...not struts. Inside the trunk, pull down the side of the carpeting near the wheel well, pop off the black cap on top and you'll see the two studs and nuts for the mount, and the large nut in the center for the top of the shock.
To "tighten the shocks" you may just need one or both upper shock insulators. As explained earlier get to the top of each shock (no strut as noted above) and remove the top nut. As you remove the nut you will find a neoprene shock mount. It removes quite easily once the nut is off. What happens is the mount cracks around its internal circumference which allows the shock to rattle or bump as the insulator allows the shock to travel up and down hammering on the frame. About $35 U.*. each as I remember. This is an easy DIY job.