Originally Posted by GabeMcG
I'm not familiar with this, if anyone has more info, it would be appreciated. A link might be even better.
The 'Search' link at the top of the page is your friend.
There are archived topics upon topics about the upper intake failing on the 3800-II engine. Basically, the upper and lower intake plenums are made of plastic. Obviously, vehicle engines cause a lot of heat over time. The plastic melts and eventually fails... most intakes slowly develop leaks and kill your engine, but some intakes have literally exploded. The remedy is to either replace the plenum with an aftermarket replacement that dissipates the heat better, or use a stock plenum and cross your fingers that it doesn't happen again. Someone else can probably explain more/better, but check some of the old threads and you'll know more about them than you ever wanted to.
Current GMs: '95 Chevy Suburban C2500, '69 Pontiac Executive
Former GMs: '83 Buick Park Ave, '73 Buick Electra, '92 Chevy Caprice 9C1, '98 Pontiac Bonneville SLE, '99 Olds Aurora, '00 Buick LeSabre