Instruments may or may not lie, but human methodology is fallible. Human sound perception can be quite incredible so if you are perceiving a difference, your methodology may need changing. Did you run your tests with your mic at multiple points, including at your ears? Did you try this while driving with that different frequency noise floor? (which also means you will be stressing your amps at a higher SPL level) Did you do this with both your prior car and this one to correlate measured results to your own sonic experience? Sound engineering is whole lot more complex than simply having a flat response at one mic position, otherwise design of speakers and placement would be simple. Mobile environments are much more difficult that home environments by at least an order of magnitude.
2018 Kia LX HEV Metal Stream with Advanced Tech