Also, have to say that I honestly trust the OPs sense of smell more than the pressure test. It's possible that when they pressure tested it that they didn't have the heater on and thus, I think, would have failed to pressure test heater core.
It could be another smell, I suppose, or they didn't really hold the pressure for all that long to see a small leak.
I'm so depressed. No one wants to come see me. :(
Mangofy your E46!