One problem related to blown head gasket has been reported for the 1999 Chevrolet Monte Carlo. The most recently reported issues are listed below.
Intake gasket blown on 99 Monte Carlo 3. 1 engine. Loosing 1/2 quart of anitfreeze per day. Mechanic has seen the same problem on 3. 1 and 3. 4 engines. Gm is using a plastic and rubber intake gasket that does not hold up. There is no updated gasket. The repair is done with an identical gasket.