What a lot of people don't realise is that NOS is not some magic way to increase power.
It is basically a chemical supercharger, and as such, it can really screw your motor up.
Sure, you see a lot of drag cars using it, but they usually have the engine re-built after EVERY race.
If you work out that a AA/FD dragster does say 8,000 RPM for most of the run, seeing as they are only racing for around 4 seconds at a time, that means the engine only lives for around 550 crankshaft revolutions before it needs new pistons and rods.
That's OK for a professional drag car, but it can spell disaster for a street engine.
I have seen a street car with NOS blow its engine sky high, when the extra fuel injector had a hiccup when the nitrous was going full steam.
Not a pretty sight.
That's one thing you have to remember about nitrous, if something does go wrong with the computer, or the fuel supply, you can wave bye-bye to your engine.
Also, the power comes on very fast, which may mean your clutch and gearbox may not last long either.
Turbochargers and superchargers don't suddenly produce another 100hp.
They build the extra power gradually over a few thousand RPM, so the extra load on the running gear is not so great.