Mikko Hirvonen surprised by Ford's improvement in Mexico

Hirvonen has tackled the Leon-based high altitude event five times with Ford, but never won. His best result was second last year when his Fiesta RS WRC was a minute and a half behind Sebastien Loeb's Citroen.

So far on this year's event, a Ford has been quickest on seven of the 13 stages completed and both factory drivers Petter Solberg and Jari-Matti Latvala have led - something Ford has failed to do on this rally for the last two years.

"I have to say it is a little bit surprising to see how quick the Ford boys are coming now," said Hirvonen. "I've been winding Jari-Matti up asking if they're running the special engine map for the whole event and how long does he think it'll last... But definitely, they have made progress from last year."

M-Sport has worked hard on the engine settings to compensate for the thinner air experienced at Mexico's high altitude by utilising a climatic chamber at Ford's technical centre in Dunton.

Latvala was faster than Hirvonen on both stages in this morning's loop, but the DS3 WRC driver feels he can control the 1m07s gap to the third-placed Ford.

"We can't slow down too much," said Hirvonen, "but I think we should be okay with Jari-Matti now."

Hirvonen is 18.2s behind his Citroen team-mate Loeb, who leads the rally.