2004 gmc envoy_sle_xl
Probably is clean then. The majority of the smoke will be created after pouring into the boost line, and from the remaining in the gas tank. The seafoam in the crankcase doesn't get burned off, it is enclosed along with the oil. I have never added seafoam after an oil change, but they say if you do it, put it in before you start the engine up when the oil is clean. Not sure that too many guys actually do that though.