I don't know that this is related to the swap. Unless I am mistaken, Ej18 and Ej22e injectors are the same size. Beyond that, since it is a MAF based car, you should still be fine because it's going to fuel accordingly and as long as you are using the Ej22 injectors there shouldn't be a problem.
There's an Ej22E driven Ej18 car here in Colorado that I helped put together that isn't having those kinds of issues. It did have some injector problems, but replacing with a good used set of stock EJ18 injectors fixed it.