Unsure of what the problem is, Litterally have no idea, Idles at around 300-500 Revs at times, & Cuts out probably once per full tank of fuel when im not accelerating, what should i look at replacing first?

I'd start by giving the Idle Speed Controller a clean and go from there if not resolved. This link has a 'How to' about 1/3 of the way down the page.