I know its a Pug and not a Ford.....Sorry!

I have bought this 306 diesel turbo. It is to get me to work and back cheaply but I found something out about these cars.....You can up the boost manually! So I have turned the max fuel screw round and turned the screw in the turbo.....It has gone from 12 psi to 17psi which gives her a nice pull......Only thing is on boost she gives out heaps of black smoke now, would this be due to the max fuel screw being wound round to much?!