probleme with physics fire for mclaren 2010 engine sound

hello,

I usually play with the original physics, but to play with the sound engine "mclaren 2010 " by Mitsuro sano, I installed a new physics file.
my problem is that now it has totally changed the behavior of the car and the performance of AI.
I would like to know if we can keep the engine "mclaren 2010" which uses a specific file, while keeping the original physical game?
thank you