It can take a bit of work but you can make an improvement by making sure all sound files in a game are in the same format. A mix of 22kHz and 44kHz, 8bit and 16bit, etc., places an extra load on the sound system as it must convert to a common output "on the fly".
Unless it's all samples at 48Khz 16-bit, I suggest not to bother with this.
While I agree that all samples at same (highest possible) sample-rate would be better (mostly for common sense), a decade and over ago compromises had to be done, and that's why things had been like that.
It's a practice that has been dropped in more recent years with more modern, faster hardware (and internet), but it was common practice seeing different sample-rates being combined.
It usually has to do with different aproaches for higher quality and complexity of sound, versus file size compromises - all depending on the role of the sample(s) in question (if primary, secondary, etc).
Usually when you see a lower sample-rate in use (such as 22Khz - actually 22.050Hz) in samples, it had certainly to do with lower file size (compromises of old, be it for packaging reasons or less strain on system). In most cases, with the necessity to have a longer and more complex sample (usually of secondary importance, such as background effects) but with far, far less size (important when all samples need to be accounted).
Regarding the sample-rate conversion for such process:
- If you increase sample-rate, you may achieve some cleaning of artifacts, but not really increasing the overall quality per se (the original source ditactes it).
For sure, file size will increase (no longer that important these days, but it used to be).
- If you decrease sample-rate, you can (and will, in many cases) introduce artifacts that are not aparent in the original sound sample with higher count sample-rate.
Especially in the case of engine sounds (and the "inside-car" ones are usually very delicate), it's a major reason why most audio devs try to use 48Khz at all times for these samples (and if not possible, then never less than 44Khz).
Of course, common sense needs to prevail but, in practice, with modern systems, and unless it's something really stupid, the total file size is no longer an issue. Even with a gazillion of samples in use at same time.
And same thing for usage of different sample-rates in SFX, all at same time, in combinations.
So long as you have a somewhat decent gaming PC for the game in question (with less than 10 years, in the case of GTR2), in such scenario, the sound system conversion to a common output
"on the fly" is always swift and unnoticed by the user. Really, makes zero difference in gaming performance and won't cause stuttering or audio issues, even with 30+ cars in action (yes, tried and tested thoroughly before).