V12: weird. I think it may be the geometry of your airtrap. I have too a quite high flow setup. What i noticed is:
- don't add the jet-dry (or equivalent) too soon. Put only distilled water, and wait until all bubbles are gone, apart from the very small ones that hang on the tubing walls.
- then add a small dose (just a squirt) of the rinsing agent, with the pump off.
- cap the aitrap, turn on the pump, all small bubbles are gone ! And no foaming
Of course i've got a home made airtrap, made out of hard PVC tubing parts. It doesn't seem to produce foam by itself.
Last weekend (when i installed a new WB) i made the mistake to put the additives too soon - it foamed like hell, impossible to get rid of it short of flushing the circuit.