If the fill valve refills the tank too quickly, it will not flow enough water through the refill tube to also refill the bow. The only remedies are to get a slower fill valve with full volume to the refill tube, or try shutting the water supply to yours so the tank fills slower, but the refill tube still delivers a full stream.
Thanks for the suggestions. I will try partially shutting the water supply to see if that helps. If that fails, my plan is put the old fill valve back but replace the cap assembly with the one from the new valve. If that fails, I'm going to order a 528T fill valve. Beyond that, I'm out of ideas.
Regarding the vaIve filling the tank too quickly, I am wondering if that is what Korky means by "Higher refill ratio for optimum performance in TOTO toilets" in the description of the 528T fill valve (I used the 528). As pointed out in other threads, Terry has reported success using the 528 in Toto toilets, but the question of what the difference is between the 528 and 528T seems to remain unanswered.