im guessing if you know cylinder 6 is missing you got someone to pull codes for you?
the #6 injector might be sticking. cheapest way to try to fix it if its not bad is some fuel injector/system cleaner. I like lucas tune up in a bottle myself. run that with some high octane fuel. see if that cleans it up. also check the gap on the plugs, just in case. did you have any o2 sensor codes? they have a life span that can't really be pin pointed, anywhere from 50k to 100k just depends on where you get ur gasoline, climate, driving conditions etc etc. if the car has more than 70k id replace them anyways just for longevity purposes. with the raw fuel smell out of the tailpipe u gotta bad rich condition, even if the o2 sensors are good now they wont be for long.
the stuff above is the cheapest and easiest trouble shooting, aside fromt he o2 sensors which are about 50 bucks a peice.
another thing u might wanna replace is the fuel filter if you haven't already. they're typically only good for a couple oil changes anyways, thats something people overlook quite often.
OH and take the air filter out and see if therei s any large debris. i dunno about the 4.6 but on my 5.7 ls1 i gotta peice of cardboard that sucked up through the intake track and was stuck ont he filter element and i was missing on cylinder 8, car was sputtering and i was running really rich. another free troubleshooting check. (while ur at it check out
TCCoA.com - Thunderbird & Cougar Club of America technical articles and remove the air silencer if you haven't already
)
good luck and report back bud, we'll get u back on the road in no time.
Travis
94 t-bird ignition/electric 
Linear Mode
