Exhaust Smoke

[ces]

Hi to all,

Came back on long journey yesterday and had been sitting at speed not in excess of 110 for couple of minutes, rest of time 80ish, looked behind and seemed smoke out of back and as powered off, no warning lights on, no loss of power before or after, no engine temps above normal. Car done 120k miles, always serviced to schedules and never driven hard from cold. Had new catalyctic converter 4k ago, and next service now due. Anyone had similar or clues, as did not repeat it, when 10 miles later tried to power up and let off again? I am sure if it was exhaust gases, was from my car, as stupid as that sounds and as on motorway, sure there was not smoke drifting from elsewhere. Car GS300 2001.

Thanks for any help

[Noel]

Diagnosis depends on the colour of the smoke?