While driving last night the car suddenly began misfiring pretty severely. I don't have any explanation why.

The IMRCs on the car have been leaking some air, but this hasn't caused any symptom this severe to date. Could the o-ring have failed so suddenly and dramatically and cause this.

Other than that, I'm stumped. I just put the Actron scanner on the car and pulled no codes other the:
538- Insufficient RPM change during Dynamic Response Test
(Engine Run Self-Test).

632- Overdrive Cancel Switch(OCS) –
no switch action detected during Engine Run Self-Test.

I just refilled the gas tank with 93 Premium and added a bottle of anti-freeze in case bad watery gas was the cause. This failed to solve the problem.

Any ideas?

give us some more info, like, when was the last time you changed the wires, plugs... etc.

What about plug wires? Had that happen last year.. car ran $hitty...

First code is usually a sign of bad IAC. The computer is commanding an rpm change and its not seeing it. Second code is prolly a false reading. Normally when you do a self test, the computer makes you step on the brake, turn the wheel half way, and cycle the ocs switch. If you didn't cycle the switch, it will give you a code.

I would check your plug wires, to make sure none of them are shorted to ground or shorted to each other. These two would cause severe misfire. Also, check your fuel pressure. A lean condition due to a faulty pump will also cause a misfie.

Plugs. under 7k miles.
Wires. under 15k miles.
IACV. under 10k miles.
And the pump was replaced about 20k miles ago as well.