Ok... I'll start with your stated plans:
Throw your 24# High Impedance injectors (if they are actually high imped) in the garbage or sell em on ebay.
Long tube headers.... check
They're always a good mod and will scale well with your other plans. Plan on getting a Mini-Starter to go with that if you want the option of ever replacing the starter without having to jack the engine and drop the headers.
Get yourself a wideband O2 meter and an EEC tuner (your choice on brand but make sure it's something that YOU will be able to use).
Go straight for 42# injectors. That way you only have to buy them once. 42# injectors will scale with your mods all way through block splitting HP territory.
I wouldn't waste a whole lot time and effort in an intake until you know what heads you're going to run. Price out a good set of aluminum heads in the 185cc territory. Get some roller rockers, match the new combo to a good intake, and purchase a cam to tie it all together.
To hell with underdrive pulleys. For what? If you take the serpentine belt off completely, you'll gain 6-7 RWHP and likely cause cooling and charging problems. For a 20% under drive? Meh.
If you decide to eventually run NO2 with boost, then you'll need to tune for NO2 and boost. Otherwise... BOOM. You can pick up the remains of your motor after you've come to a complete stop.