One problem related to gas tank strap has been reported for the 2008 Toyota Matrix. The most recently reported issues are listed below.
Was driving the 08 Matrix at highway speed on interstate 90/94 west of madison WI. Stopped at rest stop and hear loud, hollow noise from under vehicle. Made it to milwaukee and brought car to Toyota dealer. Was informed one of the straps holding gas tank to car failed due to corrosion, wear & tear and age of vehicle. Was told noise was due to gasoline tank, rock and heat shield clanging against car's frame/chasis underneath and out of sight. Was told if second strap had failed it could have created fireball under car. Was told strap failure is not uncommon (really?). Vehicle repaired for $129 out of pocket expenses. Not feeling too safe about vehicle at this point in time but cannot afford a new car to replace it.