Yap had a defensive gem and made two crucial charities in the closing seconds as ICTSI survived a Cheeseball-Shark rally and gained a share of second place on its second win in three starts.
Host LBC Batangas bucked the absence of Alex Compton as it turned back Sunkist, 78-74, also for a piece of second place with Montana in the second game.
Warren Ybanez blew away a chance to become Cheeseball-Sharks hero as he muffed two crucial charities that would have given them the lead in the final 10.8 seconds.
Stephen Padilla grabbed the loose ball but lost his balance at the baseline and was forced to throw a weak pass to Ybanez which was intercepted by Yap. Quickly fouled by Ybanez, Yap made the two charities to ice their victory.
Padilla, who sizzled with 25 points including seven triples, launched a desperation heave from beyond midcourt that fell short at the buzzer as Cheeseball-Shark absorbed its second loss in three starts.
"We had lots of mental lapses in the homestretch but luckily for us, we got the breaks in the end," said ICTSI coach Franz Pumaren after the game marred by the ejection of Cheeseball-Sharks Topek Robinson and ICTSIs Dino Aldeguer for unsportsmanlike fouls late in the second period.
Robinson, formerly of the Olongapo Volunteers in the defunct MBA, head-butted Aldeguer and the ICTSI pointguard swung a fist in retaliation.