[dc_wright]

The probability of having all of your plugs or coil packs go bad overnight is virtually nil. Gas with water in it can be an overnight issue as the water is dispersed during the pumping into the tank, but settles and concentrates at the bottom of the tank after the car sits for a while.
The other thing I'd be suspecting is a failed ping sensor or be looking at the connection under the intake where the ping sensor plugs into the engine compartment harness. The ping sensor allows the DME to monitor for the acoustic signature from both an in sequence (correct firing) and out of sequence firing of each cylinder (mis-fire). When the ping sensor goes bad it sends false detonation (ping) signals to the DME and the DME tries to adjust the timing and fuel to eliminate the ping. The result is significantly retarded ignition timing and unpredictable fuel mixtures, causing the engine to run like crap, and of course you get bunches of misfire codes.