What happened: McLaren made peripheral changes to the Mercedes power unit in Lando Norris's car ahead of Singapore. The work targets a persistent fuel system problem affecting output on straights.

Why it matters: The team trailed Mercedes on Baku's long straights two weeks ago. With Norris entering the triple-header finale, straight-line output will decide Singapore points.

What to watch: Watch Singapore practice and straight-line speeds for signs the fix held.