[dumb_ricer]

Could the oil return be plugged, or did they forget to take one of the plastic covers off of it if it was new? If thats the case, the reason for the smoke could be bad seals. To find out if that is the problem, you could pull the downpipe off the o2 housing and check if theyres oil build up in there. Otherwise its a head or motor problem. As for the stall, it could be a blow off valve problem, if its venting to atmosphere or leaking.