1. Possibly an ignition sytem diagnostic plug?
2. Maybe this part of the harness is made for all Foci ignition systems, i.e. SOHC 2.0 , DOHC 2.0 & 2.3 - cheaper to make one harness & not use a plug?
I've seen this on Ford lamp harnesses - even if you do not have factory foglamps, they make one harness (w/ foglamp plugs) & leave them empty. Just my hypothesis (and worth $0.02)