[Stealthee]

It's not common, but I have seen other posts of it happening to other 3800s as well as other engine makes.

What happens is the car might lose spark and fuel builds up and causes vapors to build up in the intake, then there is spark and the spark ignites the vapors causing the explosion.

The problem is the plastic intake manifold is not strong enough to withstand the pressure from the explosion inside. The supercharged variants don't experience this issue.

It's not just GM cars that this can happen to. Any car with a plastic manifold can explode. The cast manifolds tend to be able to withstand the explosion.