What was found
AFTER TAKE OFF A STRONG FUME SMELL IN THE ENTIRE AIRCRAFT. FUMES SMELLED LIKE GAS. AFTER RUNNING QRH AND NOTICING RIGHT PACK FLUCTUATING +/- .5 PSI. PACK WAS TURNED OFF AND SMELL DISSAPATED IN COCPIT AND AFT AIRCRAFT. SMELL REMAINED IN 1ST CLASS FOR MAJORITY OF FLIGHT. BEGAN SMOKE/ODOR TROUBLESHOOTING PER CARD 2120-2367. REMOVED CABIN FLOOR PANEL ABOVE CTR WING BOX(424150) INSPECTED SADLE DUCTS ON ENG 1 AND 2. ALL CLEAN. NO DEFECTS. COMPLIED WITH WC 2120-2367(SMOKE/ODOR TROUBLESHOOTING) COMPLIED WITH WC 2120-2368 (AIR COND SYS OIL CONTAMINATION CLEANING). CABIN FLOOR PANEL ABOVE CENTER WING BOX INSTALLED. COMPLIED WITH WC 7100-2619( PNEMATIC SYS DUCT BURN OUT) A/C OK FOR SERVICE.