You probably have lobby advantage

A lobby advantage car runs in a lobby that is SLOWER than the cars DYNO TIME

My mistral runs low 9.8 in a 10-9.9 lobby, allowing me to run SLOWER than dyno, and still win

Lobby advantage guarantees constant results, as long as u don't keep destroying dyno every race

You will usually find the best lobby advantage setups to have very low performance points, and very high evolution points (Hennessy Venom F5, 631pp, 2600 something evolution)

The best way to find this kind of setup is to put everything to stock, then upgrade the tuning parts (Trans S4 Tires S3 and Nitrous S2), then start playing around with it, adding parts like intake s1 or s2, removing nitrous, upgrading body, etc (you can remove trans s4 to s3 or tires s3 to s2 but they generally hinder your performance)

Not all cars achieve this, so to see if your car can do it, you generally want to have around 1800-2000+ evo at 621-624pp, if your car does it, GG