After a strong rev. up of the engine (during an emission test) our 3.1 Vin D Pontiac TS started to run rich.
Now there's an awful smell coming from the tail pipe, lots of gray smoke, the snow in the back is getting black and the engine is hesitating when you press the gas pedal.
I've just changed the EGR valve but this didn't improve things at all.
The plugs, Bosch, changed 2 years ago, are fouled (just cleaned them up). Oil, changed 2 months ago, is already diesel-black.
The air filter, spark wires (ACDELCO), distributor cap, rotor and ICM are changed recently. Cooling system is ok (new thermostat).
Any ideas where we should go from here?