As said circa 280BHP is stage 1 and just requires remapped chip and a uprated actuator, to get 300+ your looking at stage 2 so that means the above plus a 3 BAR MAP sensor and uprated injectors, I.E Siemens 55LB or Bosch 803's (Dark Greens) and uprated breather is a good idea.

However due to the cost difference people normally jump the gap from stage 1 and go straight to stage 3.

Martin