I know this is a bit of a late response, but have you tried the Foot Pursuit Aid by Albo1125? You can configure it a bit in the ini to even go a tiny bit faster. Its a tad bit more realistic than shooting the suspect in the leg, although I do it on purpose most of the time when they are cuffed if I am pissed lol. As far as the despawn of the vehicle goes, its hit or miss with me. most of the time its there if I can tag a suspect within a reasonable distance, so ya use Albo's mod mentioned earlier. See if that helps. There is also a persistence mod out there that literally allows for bodies, vehicles and various other objects to remain stationary no matter what the case is unless its hauled away or stolen etc. Problem with that mod is the memory it starts to eat at your PC after awhile. Because dead bodies will stay lying on the road 3 blocks over for hours. If you play that long.