Where's Antifreeze Going?

I have a 190E 2.3 with 130,000 miles. Within the last 6 months I have replaced the radiator, the water pump, the auxiliary water pump, the tank cap, all the hoses (except the one at the back of the head which goes to the heater core, which I can't figure out how to get at the end nearest the firewall.)

After all this, I am still losing anti-freeze. I cannot see any evidence of leakage, nor am I seeing any evidence of anti-freeze in the oil.

I'm stumped. Where's it going? The engine runs great. Am I looking at a head gasket leak into the combustion chamber? I would have expected evidence of that coming out the tailpipe in the form of continuous white vapor.

Any suggestions? I have not had a pressure check since doing all these replacements, but that is my next course of action.