Parts department at MB says the 5 smaller bolts holding the recycle covers in place are "one time use," should be replaced when covers are serviced. They snap of easily. Sensor safe RTV should be used otherwise you may ruin an oxygen sensor or two, it happened to my '06 when the dealer resealed these covers, check engine light came on less than 50 miles from the dealer. They replaced 2 sensors under warranty. A couple months later when replacing air filters I noticed one of the small bolts was snapped off, the cracker jack mechanic had to know that it left the shop that way.