I have a 95 Z28 street car that had NoS on it before I bought it. Everything is still in the car except the fogger that went in the rubber intake in front of the throttle body.

I haven't used nitrous before and I'm wondering how a 125 shot would affect the engine. I understand that tuning is detrimental so that would be important not to lean it out.

But I'm guessing the electronics or ignition would handle this with a injected engine??

THe car reads 85k on it, but I know it has been run hard. Doesn't smoke or misfire at all.

As long as it's set up as the manufacturer designed it, with timing specs etc., you will be perfectly fine. Those little injected car systems are real conservative and work pretty sweet, easy way to add 100+ horse.
Who was the manufacturer? Just get the parts to complete the system as it was designed originally and use the settings they reccomend and you will be good. I wouldn't mix manufacturers especially if you don't have good knowledge of tuning nitrous, it's fun but can be very unforgiving.
Hope that helps.

Wet or dry system? Do not geuss your fuel pressure check and make sure . It will be fun with the right tune up .