Disconnecting the EVR electrical connection would be the easiest way to consistently pop a code on a 96 without damaging anything (provided you don't run the engine so hard that EGR is needed to cool the engine). The gas cap should pop the code reliably, but some old PCM calibrations have a fairly poor completion frequency for the test that detects that fault (the PCM only looks for EVAP faults under very strict conditions due to all the variables that affect EVAP pressure changes).
If you are collecting the actual J1850 messages with a monitoring tool, I would be happy to review your messages. I am the PCM communications specialist for Ford assembly plant testing.
1999 Contour SE Sport MTX75 T-Red/Grey
Audio: Pioneer DEH-7400MP (MP3 CD), Pioneer TS-A6857 front & rear, PPI PCX-250, Infinity Perfect 10.1
Other: cup holders, cargo net, Blizzaks, Potenza RE950s
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