Two or three questions:

When you say no start, do you mean it cranked over but wouldn't fire?

When you say lean, how do you know this? If you are monitoring the A/F using an obd system via the stock O2 sensors then it will not give accurate results. By this I mean it could be lean but you don't have an easy way to know how lean it is whether it is dangerously lean or not.

What is the NOS EFI kit, a nitrous kit?

If it is a nitrous kit you need to probably make sure it is sealing around the nitrous injector/s so that it isn't drawing in unmetered air. Also, I would disable all your aftermarket stuff until you have the car working ok on the stock injection system. Pinging can be caused by low octane fuel so put some octane booster in it.
Don't forget to check/replace the fuel filter as well.

warmonger

Former owner of '99 CSVT - Silver #222/2760 356/334 wHP/TQ at 10psi on pump gas! See My Mods '05 Volvo S40 Turbo 5 AWD with 6spd, Passion Red '06 Mazda5 Touring, 5spd,MTX, Black