"Performance modifications" refers to changes made to a vehicle or machine with the aim of improving its speed, power, efficiency, or overall performance. Full definition
There might not be any extra power but the M Performance modifications have the capacity to change not just the way the M2 looks but how it drives, too. (evo.co.uk)
My car had several performance modifications and was in the 400 hp range, 0 - 60 in under 4.3 sec. (edmunds.com)
They have released a range of performance modifications for the AMG GT that are best showcased by the mental flagship 825 - bhp AMG GT R R825. (carbuzz.com)