If you haven't already looked, hit F11 twice to see the bounding box. Maybe you can fix it by changing Use_box or use_AABB.
You can also change it by setting the dimensions in the car's action.
Look at the model in MED and check the dimensions at the bottom of the screen.
As you move the cursor to the front or back of the car you'll see a plus number and a minus number.
In the action, add:
my.fat = on; //you have to use both fat and narrow
my.narrow = on;
wait(1); // wait 1 frame after creation
vec_set(my.min_x,vector(-50,-50,-50)); //x,y,z negatives
vec_set(my.max_x,vector(50,50,50)); //x,y,z positives
Hope that helps.
