white smoke-coolant-you have coolant leaking internally causing it to be burned
black smoke- fuel- too rich baby, your dumping more fuel than it needs! that stuff is expensive fix it
blue smoke-oil- oil is leaking internally causing it to be burned. now there are several time it could smoke:
1. just for a sec. at start up you can be 95% sure you have some bad valve seals
2. on decel. after revving it up coming down with the rpm rings my friends
3. all the time time to up grade to the 686 kit
someone pmed me to ask this so i figured id post it. hope it helps someone