Lots of smoke after oil change on 1990 Porsche 911

I took my 1990 C4 Cabriolet to a local repair shop for an oil change. They replaced the filter and pulled the drain plug and per the owners manual added 6.5 qts, let the engine idle and tried to add the additional 3.5. They couldn't get more than 8.5 qts total into it. At idle it was overflowing from the reservoir and would go down when opening the throttle. When I tried to drive away it start bellowing smoke out of the tail pipe. They used synthetic 10W30 oil. I left it there for now and am thinking I need to have it hauled to a mechanic. Any ideas or suggestions would be greatly appreciated.

Asked by for the 1990 Porsche 911
sounds like something may have gotten clogged, I'd take it to a porsche spec shop and have them look at it since they'd know better wahts going on than a reg shop