I have just put my new scorpion exhaust on my px 200 and running a 122 jet the colour of the plug is black sooty what next ? and also it is a little spluttery through the gears.

120 main, 2.5 turns air screw, b9 plug

Drop timing back to 18 aswell

The black plug colour and spluttering are usually caused by the motor running too rich.
The 122 may be a bit too much, you could try reducing it, maybe a 120 main.
I ran the standard 116 on my 200 with scorpion and it was fine, but they are all different, its better to be safe than sorry. Keep an eye on the plug.

Good Luck