2015 z06 lt4 a8 STOCK Corvette

hello,

application is Corvette VIN G5602310, odometer is KM 86.076 I did the full service to it one week ago, with new carbon rotors in the front, front & rear brake pads, engine and differential fluids, car has always regular maintenance done.

clean radiator from dust.

according to customer, after this service the car is ok from 0 to let's say 200 km/h but above that is too slow, like if it's towing a trailer, also, when he left the accelerator pedal, he feel a lot of engine braking slowing him down

according to him, this happened after the maintenance. and it's not related to ambient temperature. no DTC at all on any modules. wheels are all free to spin, no drags

any idea? the car is 100% stock, no modification

thank you so much

best regards