Odd Misfire

[Nattman82]

Well, changed the air flow meter over for my mates which was working fine in his car but it made no difference.
On the way home I noticed a few more details to the issue, when the car is missing/hesitating there is black smoke pouring out the exhaust but when the boost comes in all smoke goes away and the car pulls as normal. Also, the problem is significantly reduced when the car has full warmed up and has been driven for a while. I took the plugs out today and apart form being a bit sooty they're fine.

So now theres a vast number of things to start guessing. Gonna start with the cheapest bits and go from there.