I just took a very brief look at your project (plan on digging deeper later) - the first thing that I noticed is that your computational domain is very small / its boundaries very close to the vehicle:
that way the result fields will interact with the inlet, the sides/top as well as the outlet which will skew the results. This is an image from @Maciek's post:
Here you can see nicely that if you go along the boundaries of the domain, the velocity magnitude almost doesn't change anymore. However if you would now shrink the domain closer to the vehicle like in your case, the boundaries would interact significantly with your results fields.
Long story short: I'd give the bounding box a couple of vehicle lengths upstream and downstream as well as sides and top.