Hi there,
I have chased down the problem to be a dodgy O2 sensor. The main problem is that the car runs rich, blows a lot of black smoke & drinks more fuel than should. Also for the road worthy it had surges/flat spots between 3,000-4,000rpm. Which were fixed with the new O2 sensor.
Basically I wanted it for a road worthy to remove the flat spots as I thought it would make the car drive a little more "normally" with the mods done to it, but as said, the O2 sensor did the trick.
I'm still chasing an Air Flow Controller, but I'm battling through the Road Worthy and an oil leak before I'll have the money to buy one. So thanks to everyone who PM'd me. I'll be in touch once I have everything sorted.