Vauxall zaffira petrol engine 1.6...put to much oil in engine,got it drained and refilled about 4 days later,was told it would stop smoking after a couple of days which it did,cars performance is no where near what it was and there is a burning rubber smell cominf from exaust but not from under the bonnet?

You have given a general idea as to the excess oil etc. When you over filled the engine, did you drive it around for the four days?
Excessive oil in the crankcase will rob the engine of power. The crank has to "beat' it's way through the oil etc which acts as a brake. As you have drained and re-filled the oil, it may prove beneficial to inspect the crankcase breather and all other piping in the breather and engine re-circulation systems, as you may have a dose of engine oil fouling them. Some have metering apertures and the oil will plug them and as the underbonnet / hood, heat rises the oil in the breathers will start to bake, and offer further restrictions.

Other effects of over oiling will be crankcase pressures rising and gaskets being unable to cope. This will lead to gasket leakage, and you may now have an oil leak reaching the exhaust /cat. The engine will also "pump" oil into the cylinders and that oil will travel down the exhaust pipe, (internal), If you have a cat on the car, the oil will coat the internals and render the cat useless, with the attendant faulting of the ECU system.

Unfortunately, later model cars depend on each item of their systems working correctly to achieve any sort of efficency. It only takes a small 'hiccup" to affect every working system.

May take about 100 miles before things get back to normal,if the plugs got oiled,try adding petrol additive(injector cleaner)in 5 gallons of petrol and you may be suprised how much smoke you kick out...(oil in exhaust system).