Black Smoke But No Pings

Last month I had a Vortech supercharger installed and things have been running great. The only issue I had was that I had a little detonation under very hard excelleration at higher speeds. If I down shifted from third to second (say to roast your friendly neighborhood F-Body), rpms at 4000 and I punch it, I'd get some detonation, nothing too major, but some. Same situation going from 4th to 3rd. I never got any in 1st gear under any circumstances. I was going to take the car back to the shop I had the sc installed at and they would correct the issue. Prior to doing this I have had a completely new exhaust system installed, X-pipes and high flow single cats on each side, 2.5" all the way back. The speed shop said to do the exhaust system before bringing it back as they'd reprogram the computer for a higher fuel rate now that I've got a better breathing exhaust system and they'd corrrect the pings. However, once the exhaust system was done, I haven't had a single ping under any circumstances and I have not any reprogramming done of the computer, which is great! Only questions is, when I start the car a get a small puff of black smoke and I think I smell a little unburnt fuel. I didn't have this prior to the exhaust work, I think. My questions are 1. Why would the detonation go away after the new exhaust system was done (I'm using the exact same gas stations and premium fuel) and 2. What is now causing the black puff of smoke at start up and is it a critical situation where I need to get the car retuned asap. Sorry for the long story, but any input is appreciated. Thanks!