Intake Manifold water leaks

My 2000 Silverado 4.3 is starting to have a problem similar to a 97 Olds 88 we used to have. The throttle sticks in the closed position and it takes a hard punch to loosen it. When this happened on the Olds we found that the upper intake plenum had a coolant leak and the lower plenum was full of a coolant. This apparently was a common problem on the 3.8 V-6's, and GM made a change to the intakes to eliminate the it. Does any problem like this exist with the 4.3?

you need to clean the throttle body plate with carb cleaner, when was the last time it was done? recommend at least every 30,000 miles.