Mark Webber testing the latest 'trick' Red Bull on Saturday

That is the claim of Germany's authoritative Auto Motor und Sport magazine, after the radically updated model made a troubled debut late last week as the pre-season test period ended.

Rivals and pundits believe the reigning champions are still leading the field, but the latest Barcelona-spec car - featuring a significantly different exhaust layout - did not complete many laps.

Moreover, it also did not appear fast.

"When I watched Webber's long run on Saturday afternoon," said an engineer for a rival team, "it was nothing special -- not the lap times nor the tire wear."

Also unconvinced are the drivers, with Mark Webber saying the new car did not feel "massively different" to the earlier launch-version RB8.

Sebastian Vettel, meanwhile, was dead last after just 23 laps on Sunday, and is quoted as saying: "It wouldn't be fair for me to judge the upgrades, so we have to rely on the data collected by Mark."

Another rival engineer said there is visual evidence that the exhaust gases on the revised layout "are not going where they (Red Bull) want them to go".