IMSA late Thursday confirmed Balance of Performance adjustments for a variety of Prototype, GT Le Mans and GT Daytona cars ahead of next weekend’s Brickyard Grand Prix at Indianapolis Motor Speedway.

After struggling to match the power of OAK Racing’s Nissan-powered Morgan in the last two rounds, the HPD ARX-03b has been given a 0.3 mm larger air restrictor.

No other changes have been made to the P class cars.

GT Le Mans, however, has seen a significant overhaul, with either weight, power and rear wing adjustments for four of the five full-season competitors.

The Porsche 911 RSR has received a 0.7 mm increase in air restrictor, while the Ferrari sheds 30 kg, gains a 0.6 mm larger air restrictor and adjustment in the height of the rear wing.

The Corvette C7.R, which has won the last four races, gets 25 kg of additional weight, while the BMW Z4 GTE loses 15 kgs.

Additionally, the Porsche is permitted to use a 25 mm larger front splitter and reconfigured rear wing, while the Ferrari can run in its 2011 rear wing profile.

Fuel capacity changes, meanwhile, have been made in GT Daytona, which sees the Audi R8 LMS gain 3 liters, the BMW Z4 GT3 at a 5-liter additional capacity, the Dodge Viper GT3-R at a 6-liter increase, but with the Aston Martin Vantage GT3 receiving a 2-liter reduction.