Yes, the Komatsu 930e isn't available in this website.this isn's true i test it out. You don't need the add police mod if you got the komatsu from here, mm2x.com.
A low parameter matches a low number for each car tuning value, and an high one matches an high number.But what's the difference betweem low and high param. every time I only tweak this, the car makes wheelies. I did high and low param x2(doubled)
Make some tries, so you can understand better all the modifies that the program allows.