That "huffing" sound? Turbo fart. You spool up the turbo and it makes boost and when you lift off real quick, that boost has nowhere to go but backwards through the turbo and out the air cleaner. Normal.
The black you see is not. Places to check are:
The turbo to y-pipe connection. Check around that connection with a mirror and a flashlight for the presence of soot. You will probably see it on the clamp. What typically happens is that when it was assembled, the y-pipe was not fully seated in the turbo inlet flange. Then the clamp was tossed on and whoever did the job thought the clamp would pull the connection together. It won't. If you see the soot, I would get a new clamp, take it back apart. Throw the old deformed clamp out. Slide the new clamp on the turbo as close to the body of the turbo as you possibly can without it being on the turbo flange. Get the y-pipe seated all the way into the turb. Use any means you have to, crowbar, long pipe anything. Once the y-pipe pops into the flange fully, hold it there and get the clamp on the connection and tighten it to spec while keeping inward pressure on the y-pipe. It can be a real fun thing.
Next, check for soot at the connection between your new up-pipe on the passenger side and the y-pipe. There is supposed to be a metal gasket between them at that spot. If you see soot around that connection, either they left the metal gasket out or they didn't tighten it down good enough. Getting that metal gasket in there is not easy without taking the turbo back out of the way. Don't ask how I know.
The other spots to check is the y-pipe expansion joints. Look for soot build up on them or on the firewall behind them. If you see that, its time to replace the y-pipe.
The last, and least likely spot is the downpipe to turbo connection. This connection is easy to get right. The tab welded to the top of the downpipe pretty much holds the pipe right in the right spot. If someone was sleepwalking when they assembled it, I suppose it could be possible they got it wrong. Check around the clamp for soot, if you find it, get a new clamp.