1992 Chevy Corvette missfiring above 400 RPM

Oxygen sensor
Dirty fuel injectors (cleaning the injectors often fixes this).
Bad MAP (manifold absolute pressure) sensor
Bad TPS (throttle position) sensor
Bad or dirty MAF (mass airflow) sensor
Low fuel pressure (leaky fuel pressure regulator or weak fuel pump)
Vacuum leaks (intake manifold, vacuum hoses, throttle body, EGR valve)
Bad gasoline (fuel contaminated with water or too much alcohol)

Sometimes, what feels like a hesitation is actually ignition misfire rather than lean misfire. The causes of ignition misfire may include:

Dirty or worn spark plugs
Bad plug wires
Weak ignition coil
Wet plug wires

If you don't mind, I'd like to add a word or two.

First, who replaced all of those components? If this was a shop, then I suggest you never work with them again, as this is an extremely unprofessional practice.

If you've done the work yourself, then I'd like to advise that's it's never a good idea to hunt for problems by replacing parts, because it never works and only costs big bucks.

Now, as for diagnosing a misfire (ignition or lean), rasmataz basically gave you the areas in which to look. But always begin at the simplest and work your way to the more complicated stuff. And when you suspect a faulty part, test it before buying another one and replacing something that wasn't bad to begin with. (Why I recommend not working with the mechanics who replaced your other parts)

Real technicians inspect before replacing. We know there's no pot of gold at the end of a rainbow.