I have a 1993 bmw 318i with 220,000 0n the clock. rough idol.

six months ago had new lifters,camshaft, head gasket, water pump, and all belts replaced including timing belt at huge expence. i went to start it thismorning and had trouble getting it to start and when it did motor shook very bad and white smoke poored out of exhaust.was very cold morning so may have been condensation. when warmed up ran fine and no more white smoke. still idoling very bad but only when at a stand stiill.idoling seems to be getting worse and allmost stalling.car stiill has plenty of power. changed spark plugs but no better.doupt if fuel filter was changed by previous owner so purchased one and am yet to fit it. i use an expensive motor oil and check it often and top up as motor leaks small amount from bottom of motor. coolant requires top up sometimes but very rarely. apart from rough idol car runs fantastic. if you could give me any advise i would be very gratefull.