What was found
YYT - FLIGHT 2507, THE CREW REPORTED A BURNING SMELL THROUGH THE PACKS WITH THE APU RUNNING. MAINTENANCE INSPECTED THE AIRCRAFT AND PLACED THE APU ON MEL 49-00-00 CAT C CONTROL NUMBER 141634, AND THE AIRCRAFT WAS APPROVED FOR RETURN TO SERVICE. ON 03/20/08 FLIGHT 2017 THE AIRCRAFT LANDED AT IAH WHERE MAINTENANCE OPERATIONALLY CHECKED THE PACK SYSTEM USING THE APU WITH NO DEFECTS NOTED. REMOVED THE MEL, AND THE AIRCRAFT WAS APPROVED FOR RETURN TO SERVICE.