Fuel pump is the BIGGEST problem mate, even more so than engine condition!

If you havent got an 044 on there dont even bother thinking about nitrous IMHO, the standard pump just cant hack stage 3 power + nitrous after its 10 years old or more.

Single injector would be my preference for a small dose, but there are pros and cons to both single and direct port.

A maximiser is always a good idea if you have a wizards of nos kit, if you have any other make kit though do NOT run one as you will knacker the solenoids.

As for "what can you run" the main thing determining that if you know what you are doing is spark strength.

There are wires on the L8 ecu you can ground to take timing out of it, so Det shouldnt be an issue even if you are putting 100bhp or more into it if you know what you are doing.