A mod should be able to help you move the thread. PM Darkone or code red. Road race engineering should have a calculator to help you figure out what size injector you need. Again, keep in mind that those are usually meant for 93, so increase by 20-30% for e85. I'm not sure how nitrous is going to impact your octane rating since I haven't run it, so I can't really give good advice on how to account for that.

Regardless, the injector size needed is a function of the horsepower you want, the pressure you plan to run (most cars run 43psi as that's what injectors are rated for), and the bsfc of your engine. You take the output of the formula and then compensate for fuel type that you're running. Whatever number you get at that point is the minimum injector size capable of supporting your power level at 100% capacity in a perfect world. Now figure that you want the injector to use no more than 80% of it's capacity to flow that amount (the number typically thrown around for maintaining longevity in the injectors). The tech articles I mentioned explain how the formulas work as well as the average bsfc for the 420a, which you'll need a rough idea of for pretty much any calculator.

My build: verttuner.com (hosted on my blog)