I've thought ahead on the breather hoses - when I replaced the camshaft oiler tubes (a preventative measure only), I bought all the breather hose pieces and replaced them. They were pretty well fossilized from the heat of the engine.

I really believe that smoke after accelerating and the movement of the dipstick tube during a repair are just too closely linked to be a coincidence. The car has other leaks - but none causing clouds of smoke after heavy acceleration like this!