oil coming out of my exhaust

Could be worn valve guides.

could be one of 2 thing, you have a worn oil ring, or its time for valve seals. if its turbo there is a chance is coming from the internal oil seal. good luck.

Could be a number of things. What colour is the oil smoke, blue or white? You could try a local Porsche specialist (not main dealer) and ask them to do a compression or leakdown test. Could be piston rings, valve seats, valve guides, oil seals. What is your oil consumption like? Mileage on the motor? Age of the car? Do you do a lot of short journeys? (not good on the older air-cooled motors)