Exhaust Smoking

[ReaperGFX]

so my car had its Mot on monday passed and it sailed through without any problems, the mot sheet was clean which i thought was not bad for an 01 celica,

anyway since i was away for the week which i am normally now i havent had time to change the thermostat so i got them to do it, not a problem ,

anyway i noticed before the car went for its mot once ive drove the car and stopped and switched off the ignition that my exhaust was still smoking, and i came to the conclusion that some oil was burning in my cat, i was too late to even remove the cat to inspect as i was flying out to germany,

i got a phonecall saying the car was fine and its passed,

anyway when im driving it ive always noticed that smokes coming out i wouldnt say its white but its just coming out in large proportions, i took it on a long drive today and when i turn the ignition off smokes still coming out as if someone had threw a lit cigarette up the exhaust to give you an idea on how much smoke is coming out,

i spent a good 15 mins before returning to my car and yet i could still see traces of exhaust smoke.

any ideas ?