I'm sure someone's seen this and commented on it before. Just noticed for the first time. Had my son start the truck while I was under the hood. Noticed a puff of black smoke upon ignition under the hood near the back of turbo/air intake vicinity. Only happens on startup. I'm thinking that there's a gap in the mating surfaces where the turbine elbow meets the exhaust downpipe and exhaust is escaping. Recently replaced the turbo and had a little trouble mating the original turbine exhaust elbow back onto the downpipe. Could be the down pipe/eblow fasteners aren't tight enough. Might take a vid and slow it down to see exactly. Thoughts?