The British Touring Car Championship has made changes to boost levels and centre of gravity measurements ahead of the Snetterton round, with BMW competitors set to be disadvantaged by both.
BMW's all-new 330i M Sport has won nine of the first 15 rounds this season, and defending champion Colin Turkington leads team-mate Andrew Jordan in the drivers' standings.
Ahead of the second half of the season, all non-BMW-engine cars have been given a turbo boost gain of the minimum 0.02-bar increment, which equates to approximately 4bhp.
Although Team Parker Racing competes with the older-shape BMW 1 Series, Oulton Park race three winner driver Stephen Jelley will also be affected.
This is the second in-season change boost levels, as the BMW engine was restricted by the minimum of 0.02-bar ahead of the Croft round.
BTCC chief executive Alan Gow told Autosport: "We [have done] a minor boost adjustment, like we did [at Croft], but that was all engines bar the BMW.
"It's the same adjustment, only this time we didn't take them [BMW] down, we put everyone up."
Following the return of the rear-wheel drive Infiniti Q50, which makes its first appearance in the series since 2015, all other rear-driven cars have also had to make a centre of gravity change.
Autosport understands that teams had the option of either raising the ride height by 6mm, or adding 10.5kg of ballast to a car's bulkhead - with BMW favouring the ride height alteration to save both time and money.
It is understood that Team BMR has elected to both adjust its Subaru Levorg's ride height and add some ballast in order to fulfil the necessary change to the car's centre of gravity.
Gow added: "[The changes have been made] only because with the new Infiniti, and when the centre of gravity was done, it was done against the Subaru and the BMW only.
"Now that there's another rear-wheel drive car then they've had to adjust it accordingly.
"They had to make a very small additional adjustment to compensate. "These are just running changes you do through the year, clearly they are not major changes."