[Rev]

Sounds like it's leaking coolant from a coolant passage (intake manifold to head). When you put the intake back on you needed to put a little RTV around those coolant passages. It's also easy to get the intake gasket moved into a non sealing position when you place the intake on the heads. I'm not 100% sure that this is the problem, but since you removed and replaced the intake manifold, that would be where I would look first.

Rev