On Thursday in the Principality, the RB9 did not look like a competitive car.
"We were one second too slow," Dr Helmut Marko told Servus TV.
But by Saturday, Sebastian Vettel was disappointed to have just missed pole position.
Marko said Buemi, Red Bull's Swiss test driver, had turned no fewer than 400 laps in the simulator at Milton-Keynes, seeking a solution.
Buemi then headed to Monaco, and according to Auto Motor und Sport, he was spotted at Heathrow airport with two huge boxes of baggage -- reportedly new front wings.
"On Saturday we were on the pace," said Marko.
"After the initial problems, we are more than happy with the result -- we have been able to extend our lead in both championships," he added.