I agree with these guys - if visible soot is present it needs a day with my girl friend AKA lead foot.
Should a good blow out not clear it might be worth mentioning seeing the mileage there, is also an
valve (exhaust gas recirculation) a rubbish idea that on higher miled cars needs a good clean out along with it's surrounding parts - not a particularly hard job, it takes about 2 hours and simple tools (half decent socket set really).
it re-circulates some exhaust gas to reduce emmissions and aid with the heating up of the engine - it closes when at optimum temperture.
A nifty trick I learnt in the desert (okay some really helpful person told me on here) try using the AirConditioning after starting to see if anything improves - it closes the
and no exhaust gas will be entering the combustion chamber. if it does improve I suggest cleaning
and related parts.
If this does not, suspect an
leak - but that usually smokes 24/7 and when accelerating heavy. So it doesn't match what you describe.
Hope you make a good choice, best of luck!