2000 lincoln ls missing and emissions

i have a 2000 lincoln ls 3.9 ltr. and it started missing real bad and i noticed a raw smell like the catalytic converters were going bad, so i had the codes checked and it said misfiring on multiple cylinders. i put new plugs and new coil packs in it and it still misfires. i had the catalytic converters checked and they told me they were fine. i am still concerned with the raw (sulfer) smell. any help would be greatly appreciated.