MMMMMMmmmmm��.

I know how you feel�

I had a similar problem on a Honda Civic, very similar.
The front radiator was the problem; nobody (Even Honda) found the problem.
(Loosing pressure?!?! And clogged at the same time.

But you did the pressure test!!! If you get very hot you can have
overpressure.

Before going in court I can only suggest one last thing, get rid of the
coolant (all the way).
Test the radiator, a real professional test. Also, flush the entire system
and put new PF coolant. Are you overheating, are you sure!!! (Check the rad
if it's hot, do the fan go ON)

Men, men men!!!! Give it a try!

Good luck.
Ben
http://www3.sympatico.ca/huotx/engine1.htm