I have got my car(manual 1994 850) to a reasonable level (approx 300bhp) on the cheap, I have decided this is going be a keeper and I want to take it up a notch, my target is 400+ and my budget isn't much of an issue as it isn't going to be done in a hurry. I understand what I need brake and transmission wise, its just im not sure on which turbo beyond the td04 range is the most suitable? and easiest to fit, going to get rods but leave the rest of the block as it is, basically:

1. what turbo
2. which injectors
3. do I need/should i have Water/meth injection (completely new to me)
4. I know I need to change my intercooler, any recommendations

Thanks