My TL runs rough/missing when cold, it seems like it is missing and smells like it is running rich. It will continue this until it has reached operating temp then runs perfect. I can leave for a few hours and start again and idles and runs perfect, only does it on start up when stone cold until it reaches temp.

Any help in the right direction would be good?

My guess would be to check the coolant temperature sensor - the one that tells the engine if it's hot or cold and adjusts the fuel mixture via the injectors so that you have a richer mixture when cold and leans out when hot. Without a rich enough mixture when cold, the engine will miss and run roughly till warm...the missing will result in unburnt fuel going out the tailpipe making it smell like it's running rich.
Other than that, I guess it could be plugs/leads/ignition module/distr cap etc all dependant on how many Kms your car has done and the general condition of the engine. (that info would help!)

Car done 190,000. engine seems to be good condition, always serviced. I just gave it a full service including plugs, timing belt and water pump.
Will try the temp sensor, where will I find it?

I couldn't find a listing for one to suit a TL? is this correct?
Lancer CE II 4G93 98-00 1.8 4 ECI CS838
Magna TN EFI VS71V 87-89 2.6 4 ECI CS826
Magna TP EFI V571V 89-91 2.6 4 ECI CS826
Magna TR EFI W592Y/W532Y/W531Y 91-
94 2.6 4 ECI CS826
Magna TS EFI W531Y/W532A 94-97 2.6 4 ECI CS826
Magna TR Y721A 91-94 3.0 V6 ECI CS823
Magna TS EFI Y721A 94-97 3.0 V6 ECI CS823
Magna TE EFI 4G64 96-97 2.4 4 ECI CS838
Magna TE EFI 6G72 96-97 3.0 V6 ECI CS838
Magna TF EFI 4G64 97-98 2.4 4 ECI CS838
Magna TF EFI 6G72 97-98 3.0 V6 ECI CS838
Mirage CE 4G15 96-00 1.5 4 ECI CS838

Coolant temp sensor is located near where the top radiator hose connects to the engine - it's the one in front and the other one with a single wire is the temp gauge sensor. I'd check it electrically before replacing if you have a multimeter - tests are at bottom.....otherwise get one from a wrecker. Cannot help you with the part number.
However, if the problem has only happened since the timing belt change etc I'd suspect that maybe it was installed one tooth off...there are ways to check this as well. Did you remove the distributer cap to check rotor button/cap and also are you sure the plug leads are 100% as it's when the engine is cold that the ignition system will break down.....once the engine warms, plugs require less voltage to fire/ignite the mixture.
Good Luck.

unfortunately not the temp sensor, still doing it but thanks anyway.

Car died the other day whie driving, had it towed to Mitsubishi and the issue ended up being distributor.