When GM was testing the ECOTEC for drag racing, they originally started using nitrous, and kept adding more and more until the engine finally broke something, easiest way to figure out weak points in a car. The rods were the first to go, at something like ~280HP, which would mean roughly a 140 shot of N20. That is definately too risky though, because you'd be pretty much guaranteed to blow your engine...
To keep things safe, I'd say a 75 shot of N20 would be plenty to try at first. If you're feeling brave, perhaps a 100 shot? I really don't know much about nitrous though.. but apparently wet systems are safer than dry systems... hopefully somebody else on the forums can help you out with that more than me...
And definately it sounds like you need to learn a lot more before you go installing a nitrous kit. "Currently the wheels on it are fine.".... <_< Well ok, if you say so....
But I don't know what you think that has to do with your engine...
And you better be sure that its a 2.2 ECOTEC, and not a 2.4 Twin Cam, because the Twin Cam would probably blow up shortly after a 50 shot of N20...