Well there is one way that i know of, it's a bit out there and difficult to do but i believe it will get the effect you want.
Before you import the car into the vehicles file, change the name of the 2 model files to FIRETRUK, then import it. This will make it so that you always be the only one riving it. (I personally have never seen a fire truck cruising down the road.)
Now after that you will want to update the handling so that it performes like a sportscar.
Find the FIRETRUK line in Handling and replace the whole line with this,
FIRETRUK 1700.0 7.3 85 0.0 0.0 -0.08 0.0 5 0.21 1.0 145.0 0.23 0.65 0.7 35.0 1.35 1.10 14.5 0.15 0.48 1.2 1.0 1.0 0.13 -0.21 0.0 0.5 1.0 1.0 0.8 1.5 0.0 25000 440000 0 0
That will make it handle like a Sabre GT. Of course you can change it to whatever you want.
Have fun
This sounds like a great idea! Thanks I'll try in a second.
Do you think the firetrucks parked at firestations will be the aforementioned car howeveR?