who told you they are not legal, as said don't put it in the middle of your screen ,have you seen the amount of **** stuck to a traffic coppers windscreen.
there is not such a thing as white smoke imho either steam or blue tint too it ,turbos don't need to have play in them too let oil past the seal, are you using oil, did you have the head pressure tested ?
most of the time with hg on the 300 you don,t get water oil mix ,
take the rocker assembly off and lift out the push rods to see if any are covered in carbon
nah the law has been scrapped all you need in France is hi-viz and triangle,the hi-vizmust be kept in reach of driver not in the boot ,the idea is you put it on before leaving the car one for each person in the car .