1988 monte carlo keeps backfiring and spitting out of the carburetor. I believe it has a vacuum leak or something to do with the vacuum. It'll run fine one day then the next it won't. Also, the transmission will also seem to shift late into second on the days the car doesn't run right. The other days it shifts fine. And it seems to be pouring white smoke out of the driver side exhaust, none or the passenger side. Burning oil? Need new plugs? What could be the issue with everything? Has demon carb, throttle body spacer and edelbrock intake with original 305

Thanks.