The vehicles covered by the GM engine recall were outfitted with the 3800 Series II design, manufactured between 1995 and 2004. They were identified in two phases. A 2008 recall of 207,000 vehicles applied only to turbocharged 1997-2003 Buick Regal and Pontiac Grand Prix models. The 2009 GM recall expanded the list to include more than 1.2 million normally aspirated versions of several GM models including the Grand Prix and Regal.
Here's the full list:
For both GM recalls, the danger comes from engine oil catching on fire after it has been spilled or leaked onto the hot surface of the exhaust manifold. If the oil catches fire, the flames can spread to plastic parts including the spark plug wiring channel and the upper intake manifolds and engine covers.
For more on the issue of recalled but unrepaired cars, please read:
Recalled but Unrepaired Cars Are a Safety Risk to Consumers
How NHTSA Gets Cars Recalled
Post-Recall Problems Pit Owners Against Carmakers