hello
the right injector in the photo with the plastic cap is from a vtec engine (ex, lx etc.) , the left one without a cap is from a non-vtec (dx models, vp etc.).
the intake manifold for the vtec has another small hole for each injector recess, the non vtec doesn't.
i wonder what's the purpose of those plastic caps and the extra holes in the manifold and whether they are interchangeable. and why there's no part number for the lower o-ring, which probably has to be replaced if you remove the injector.