The performance of the Cadillac has been pegged back for the Rolex 24 at Daytona later this month.
The Cadillac DPi-V.R has been given smaller-diameter air-restrictors in the pre-event round of Balance of Performance changes ahead of the IMSA WeatherTech SportsCar Championship opener on January 27/28.
The new 5.5-litre normally-aspirated engine in Cadillac's DPi contender has had its restrictors reduced in diameter by 0.6mm to 31.6mm after dominating the official pre-race test at Daytona earlier this month.
A Cadillac went fastest in each of the eight sessions over the three-day test, the four cars blocking out the top positions in the combined times.
Mazda, which ended up ninth in the overall times, has been given two performance breaks ahead of the race.
The Joest-run RT24-Ps have received a minimum weight reduction of 15kg and an rev-limit increase of 300rpm.
The Nissan Onroak DPis run by the Extreme Speed Motorsports squad has been given more power with an increase in boost pressure at the top of the rev-range.
There have also been tweaks to the fuel capacities of the cars to ensure equal stint length for all the cars.
The Penske-run Acura ARX-05s have been given an extra four litres, the Cadillacs one and the Nissan two.
BMW's new M8 GTE, which will be making its race debut class at Daytona, has also received performance breaks after struggling to match the pace of the GT Le Mans class frontrunners at the test.
It has received a 10kg weight break and more boost through the majority of its rev-range.
The fuel capacity of the BMW, the Chevrolet Corvette C7.R and the Ford GT have all been increased and that of the Porsche 911 RSR reduced.