I'm probably missing the obvious here, but I'll make some guesses.

I don't see how changing to fuel injection would make a difference. The guides are oiled from above, the fuel is below, so gravity shouldn't cause a wash of the oil. Ditto for vacuum, oil should be pulled into the guide on the induction stroke, it doesn't matter if it is fuel injected.

When you switched:

- did you change the valve seals? I like umbrella seals better than the postive-seal type, which cut down on the amount of oil reaching the guide (at first), but later as the seal wears, let too much oil in. I don't know if this would happen with the L16, but seems to be the case on overhead valve engines

- Did you change the camshaft? Higher lift or a more agressive profile could contribute to higher wear

- Did you change the cam follower ratios? Higher ratio will contribute to higher wear. A roller rocker is best for low wear, not sure how this works on an L16

- Did you mill the cylinder head flat? That changes the rocket-to-valve alignment on overhead valve engines, sometime enough to cause problems. I don't recommend skimming the head unless it is proved to be warped