The diagrams I have are not great for Mondeo. The box you're calling the PCM is the Auxiliary fusebox or BCM, the PCM is under the bonnet. If you can take some pictures of the fuseboxes, both under the glovebox and the one in the engine compartment it might help me track down a diagram.
Normal boost is 18-22 psi, so although our test was below that, we are confident that 15 psi would have identified a leak. My engine is Euro 4, so has the electronic actuator. The rotary actuator was at the 9 o'clock position (offside looking nearside) with the engine off and rotated to a 12 o'clock position when started.
Over Boost can be caused for many reasons, the most common ones are listed (below) Possible Cause (s) Solution. Air Leak. Fine the leak, and replace/repair pipe/gaskets. Turbo internals may be damaged. Diagnose and Repair / Replace Turbo. Foreign Matter (Impact) may of entered the inlet pipe. Replace the Turbocharger. T3CD. 945 253 933 529 36 208 830 868