IMSA has confirmed a series of Balance of Performance adjustments to three of its four classes ahead of next weekend’s Lone Star Le Mans event at Circuit of The Americas.

The penultimate round of the TUDOR United SportsCar Championship season sees a number of changes in the Prototype class.

The HPD ARX-03b gets a 1.2 mm larger air restrictor but at a 40 kg minimum weight increase, while the debuting Ligier JS P2 HPD will be in the same configuration (32.5×2 mm and 940 kg).

No power adjustments have been made to DP-based machinery, although the Chevrolet-engined DPs face a 6-liter reduction in fuel capacity, with the Ford EcoBoost-powered entries running 3 liters less than the most recent round at Road America.

The two HPD-powered P2 variants, meanwhile, gain 1 liter of fuel capacity.

Much-anticipated adjustments have also been made in the GT Le Mans class, including a performance break for the Corvette C7.R.

The Pratt & Miller-built car has been given a 15 kg minimum weight reduction in addition to a 0.3 mm larger air restrictor, while the BMW Z4 GTE has been handed a 0.4 mm larger air restrictor but with a 25 kg minimum weight increase.

The Ferrari F458 Italia, which claimed back-to-back class victories, will run with a 0.3 mm smaller air restrictor beginning at COTA.

GT Daytona, meanwhile, sees weight adjustments for the Porsche 911 GT America (-10 kg), Ferrari 458 Italia GT3 (+10 kg), BMW Z4 GT3 (+25 kg) and Dodge Viper GT3-R (+25 kg) while the Audi R8 LMS gets a 2 mm larger air restrictor.

The Ferrari also receives an adjustment in the maximum RPM, while the Porsche is now permitted to run a significantly different aero package featuring a 50 mm front splitter, 25 mm wheel arch extension and the addition of a single dive plane. It has also been given a 1.0 mm larger refueling restrictor.

The BoP changes in GTLM and GTD are confirmed for the remainder of the season, with the rules prohibiting any further changes to the production-based ranks.