Volvo Repair: smoking, 2 quarts, vacuum line

Question
I have decent mechanical skills, car has 144,500 miles, I bought it as a one-owner and it was well and scheduled maintained throughout previous owner. It is a 1986 Volvo 740 with a water cooled Turbo gas 4 cylinder. The car has a lot of white smoke coming from tailpipe which has a bad smell. I just refilled gas 12 miles before it started. First there was the smell and then it started smoke, it is coming out constant and a lot of smoke. The engine is running fine not missing or anything. The water reservoir for turbo/radiator was empty but the temp gauge did not show overheating and it took 2 quarts to refill. I thought either bad gas, although engine is running fine, or bad Cat Convertor which is consistent with smell. But, because it just started after gas fill wasn't sure.

Answer
Hi Phil,
    Interesting situation...only a few ways to get oil out of tailpipe.....First, remove all 4 plugs look at the working end and assess what is going on in the cylinders...also do a wet and dry compression test just to know for sure..Oil at cam and head are leaking into cyls down valves/guides...look at inside of tailpipe to ID the residue..Turbo may have oil ports that  leak into exhaust system...Leaky master cylinder..leaks into booster...vacuum line sucks brake fluid from booster??
         I think I covered the obvious...
     A blocked cat can do lots of weird things to the operation of the engine...on that model the cat is built into the header pipe...I'mm not sure how to test that one..
                    Happy Motoring,
                                Bilbo