Hi i have a J Reg Fiesta RS Turbo, It is completely standard apart from a stage 2 195 chip and beige injectors, I know the chip and Injectors are ok as they came out of my old RST, The problem is when i start the car it seems like it is mis-fireing but it is firing on all cilinders, it idles at about 700rpm but very lumpy, If i rev the car really hard then sometimes it starts running very sweet and at about 1000rpm, then if i take the car out it will work properly on boost, but all of a sudden it will stop letting the boost kick in and runs like a bag of crap.
Does anyone know if i need to do anything to the car when i fitted the injectors and the chip, ie fuel regulator adjustment, Maby?

Many thanks for your time and Help!