By Sarah Holt
BBC Sport in Monaco
Vettel has already won the Chinese Grand Prix for Red Bull
Red Bull's Sebastian Vettel is out to end leader Jenson Button's winning streak in Sunday's Monaco Grand Prix.
The German is the only other driver to win a race this season, in China, but is 18 points adrift of his Brawn rival.
"It is important to stop Brawn winning," Vettel insisted. "We would like to turn the whole thing around as early as possible."
Vettel's hopes will be boosted, as he will use the double-decker diffuser for the first time this season.
Red Bull will fit the new design to both Vettel and Mark Webber's cars during first practice in Monte Carlo on Thursday, which begins at 0900 BST.
The team initially protested against the split-level design, used by Brawn, Toyota and Williams since the start of the season, but had no choice but to incorporate it into their own design after the sport's governing body, the FIA, ruled the diffuser was legal.
The split-level diffusers give greater aerodynamic downforce and are said to be worth up to half a second in pace.
We won't know whether we have made a step forward or not until Saturday
However, Red Bull's chief technical officer, Adrian Newey, refused to be drawn on how much his team's performance could improve in Monaco.
"It should bring a bit of gain here," Newey said. "We are pushing as hard as we can and what it brings, it brings.
"If at the end of the first session we have concerns, then we will review the rest of the weekend.
"There is an element of risk in putting it on both cars in terms of, does it perform as predicted in the wind tunnel?
"But we've decided to take that risk - as we would rather find out."
Newey and his design team have been working hard at the team's Milton Keynes base to incorporate the new diffuser into the already competitive 2009 Red Bull.
The task was more complex as they are the only team to use a pull-rod rear suspension, which is incorporated into their gearbox design, leaving little room for a split-level diffuser.
"We've only designed it around the rear suspension that we have," added Newey.
"We had to make a small compromise on the pull-shaft and it has been a difficult exercise."
Vettel was also cautious about predicting if the addition of the modified rear would see Red Bull catch up with pacesetters Brawn.
"We have tried to bring more bits to the car which will help the performance but we won't know whether we have made a step forward or not until Saturday," said the 21-year-old, who claimed Red Bull's maiden victory in Shanghai.
"It is difficult to prove anything at this circuit because it's so different to every other track. We will have a much clearer idea at the next race in Turkey."