I just changed the oil on my 99 and did an inspection around the engine. I found a small puddle in on of the lower intake manifold valleys. Here'* a pic (I circled the puddle):
And here'* directly above it:
This is on the driver'* side, just down and across from the throttle body. This make me very angry. I just replace the upper intake, upper gasket and all lowers at 77K in May. Now, in Feb., at 103K it'* already leaking.
Stupid GM. What a worthless design. God this makes me mad.
My overflow bottle isn't low what-so-ever, but it'* just a matter of time. I guess if I want to keep this car around I'll have to put "new upper intake manifold, new upper intake gasket, and new lower gaskets" on the annual preventative maintenance schedule.