smoke=bad, 190000miles=bad, engine losing power=bad... there is one cure and it is to put your last gallon of gas in her and give her one last drive down to the junk yard.. your engine is just worn... engines lose power as they get older.. it all depends on how well you take care of them.. you could put a new V6 in there if you wanted... i dunno where your gonna find a 4.3L astrovan motor