1995 Mazda Millenia Idles High, Stalls out when Driving and

Engine Performance problem
1995 Mazda Millenia 6 cyl Two Wheel Drive Automatic

Purchased a used 1995 Mazda Millenia V6 2.5L, was running great for about 2 weeks then suddenly car starts idling high around 3000 rpm, usually 30sec- 1 minute then suddenly drops to normal 1000rpm range. Then if you get it to start, (because sometimes it will stall by attempting to put it in Reverse), it drives for a short distants and stalls out while driving. Once stalled, I must literally hold my foot on excelerator to get it to turn over, this normal takes a while, 10 mins or more and when it finally does crank up it always with a lot of "white smoke coming from tail pipe." Then it starts the same process of high idling and stalling out for short distances while driving and hard to crank with white smoke from tail pipe with strong gas smell in car (only smell when attempting to crank for prolong periods). I guess my obvious question is why does the car idle so high then drops to normal and why would the car stall out while driving, and why so hard to start up once car stall out. Please note: I have replaced Idle Control Valve, Mass Air Flow meter ( both found in junkyard) and new air intake assembly and new PC valve and still have same problem. Also, the 1995 mazda miillenia has the old OBD-I diagnostic under the hood and no the check engine light is NOT ON. I really need help and anything that could solve these PROBLEMS would be greatly appreciated.