If it is comming from the center of the intake, kinda under the throttle body it is prolly the waterpump to manifold plastic elbow or the seam in between the upper and lower intake. If it is to the left or right of the intake near the heads then I would guess the lower intake to head. The elbow and lower intake to head are both very common leak points for this engine.

Massey

 

I think I would just replace the gasket set and L shaped elbows. Make sure the water pump weep hole is not leaking as well.

 

^^ +1

Massey

 

It sounds like the water pump since it's centered on the engine.
I hope these diagrams can help. Here's the procedure for changing the water pump and lower intake manifold:

Water pump:
http://www.gmtunerz.ca/docs/02waterpump.pdf

Lower intake:
www.gmtunerz.ca/docs/02lmanifold.pdf