I have been fighting a coolant leak for the Water2Air intercooler on the FMSC supercharger for at least a year. The coolant reservoir started loosing coolant during trackdays or spirited driving.
This turned into lots of modifications like upgraded heat exchanger, new coolant reservoir with higher pressure cap, new clamps..  Nothing worked.  If anything it got worse.

Then alphagamma and chenr_nc posted similar symptoms in this thread that was caused by failing O-rings inside the supercharger assembly.
And what do you know....   1 hour job and $2 in parts and it was fixed. Did not loose a drop of coolant during the last trackday.  Small stuff like this can cause a lot of grief.

Some pics of what is involved:
Throttle body and the upper intake manifold needs to be removed to access the front coolant inlet cover:

Do not try to remove the IC as it's a fat bead of silicon gluing one side of to the SC housing.
Do not lose the small piece of gasket material in the middle as it's there to avoid rattling and movement against the cover.

The O-rings are located in the groves in the front cover as shown here:

I replaced mine with some generic O-rings. Slide them over the IC flanges to verify that they have a tighter fit than the old ones. Mine was all flattened on the inside.