DPis have been slowed for the fourth consecutive race, as IMSA works to achieve parity with LMP2 machinery in the WeatherTech SportsCar Championship.

The sanctioning body released Thursday an updated Balance of Performance table for the Prototype class ahead of next weekend’s Acura Sports Car Challenge at Mid-Ohio, which sees all four DPis hit with power reductions.

The turbocharged powerplants inside the Acura ARX-05, Mazda RT24-P and Nissan Onroak DPis will all have slightly less top-end boost, with the Cadillac DPi-V.R getting a 0.6 mm smaller air restrictor.

Associated two-liter fuel capacity reductions have been made to each of the DPis as well.

The 30.4 mm (x2) restrictor on the Cadillac DPi is 1.8 mm smaller than than the configuration it ran in January’s Roar Before the Rolex 24, and has seen seen reductions made in each race, outside of the Mobil 1 Twelve Hours of Sebring.

Sportscar365 believes it equates to roughly a 40-50 horsepower difference since the start of the season.

The changes come in the wake of a dominant start to the season for DPi machinery, which have swept the opening three races.

Only a single LMP2 car, the No. 54 CORE autosport Oreca 07 Gibson, has managed to get on the podium so far, in the Rolex 24 at Daytona.

Per its agreement with the ACO, LMP2 cars are not subject to BoP adjustments in the WeatherTech Championship, meaning IMSA has had to continuously work to reduce the performance of its flagship platform.