The eatery is popular with celebrities, with endorsements by chef Al Brown, comedian and food blogger Jesse Mulligan and musician Tama Waipara.
Some customers had been deterred by coverage of the low rating, but were slowly returning since the regrading, said Mr Li. "Some customers say we are better than before."
Business had slowed "a little bit" last month. "But people still like our food so they're still coming."
He expected patronage to pick up again. "It should be a week or something like that. When we had a D they don't [come] but we have A now so maybe they come again."
Food grades are issued according to Auckland Council's criteria under its Food Hygiene Regulations. Those criteria include overall standards, cleaning and sanitising, and staff training.
Barilla joined 28 others to hold a D grade in the old Auckland City boundaries after an inspection in May.