Red Bull team boss Christian Horner believes that the "abnormal" top speed of Mercedes' W12 was reined in by the Brackley squad in Qatar.
The fierce battle on the track between Mercedes and Red Bull has been just as tense off it in the back-half of the 2021 season.
The impressive straight line speed of Mercedes' car has prompted a whirlwind of speculation, with Red Bull hinting at a ploy exploited by the German outfit involving the rear wing of its W12 to boost its car's maximum velocity.
At Losail last weekend, Horner alluded to the Mercedes aero element flexing at speed and pointing to score marks on the wing's endplates as a tell-tale sign of bending.
Mercedes team boss Toto Wolff hit back at the Milton Keynes-based outfit's speculation, insisting Red Bull was seeing a "ghost".
However in Qatar, the FIA introduced a new rear wing load test as part of its fact-finding mission.
While the test was done for investigative purposes only and was not part of the governing body's panoply of legal verifications, Horner believes the unofficial probe was enough to compel Mercedes to perhaps tweak its rear wing to steer clear of any trouble.
"I think what we have seen in recent races is an abnormal straightline speed," said Horner.
"I think Toto has been at pains to point out that there have been gains in straightline speed when nothing has changed.
"But it's encouraging that this is the first race since prior to Silverstone we've been able to match their straightline speed and an exponential increase in races.
"I think that I am glad to see it is being well policed," he added. "I'm confident that the tests that have been introduced should eradicate any ability to circumnavigate."
Indeed, in Qatar there was only a marginal difference in top speed between Mercedes and Red Bull.
But Wolff suggested that the small delta at Losail was due to the track's layout which favoured the Brackley squad using a high-downforce aero package.
The Austrian believes Red Bull could kick up a fuss once again in next week in Saudi Arabia.
"Have they shown some data or photographs about the straightline performance?" quipped Wolff when told of Horner's comments.
"It's a track here that is less power-sensitive, and interestingly I think they've just done a good job: their straight-line speed with the big wing (high downforce) is identical to ours.
"So yeah, I'm happy that they are happy.
"Let's go to Saudi Arabia and maybe we'll hear some comments again. In a way, the debates that are being kicked off or launched, I cannot follow any more.
"I have taken the decision for myself and the team that we're struggling to keep up with commenting on the rumours that are being made from that side."
Queried on how the title fight may unfold in the final two rounds, at Jeddah and Abu Dhabi, Horner believes small margins will decide the championship's outcome.
"I think it's going to be tight," he said. "The next track arguably should favour Mercedes but Abu Dhabi, with the modifications made there, who knows?
"Going into these last races, we have an eight-point lead in the drivers' championship, and we've reduced the gap in the constructors to five points.
"So both are fully in play. And that's fantastic because we're now at the climax of this world championship."
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