What was Lando Norris' top-speed problem in Baku qualifying?

Lando Norris qualified fifth for the Azerbaijan Grand Prix in Baku after a technical problem severely hampered his McLaren's straightline speed. Despite outqualifying teammate Oscar Piastri 9-1 in the previous 10 sessions, Norris was three tenths adrift in Q3 — his worst deficit of the season. Norris confirmed post-session that his MCL40 was requiring more effort than Piastri's car, suggesting an unresolved mechanical issue beyond McLaren's usual straight-line speed deficit to Mercedes engines.