The texture is a little uniform, but shader would need a lot of work to make it look good with anything else, since they're all being drawn in the same orientation. Maybe replacement of the single smoke frame with an array of them, selecting one at random for each particle. And simulating actual smoke is a huge pain in the behind... I've seen papers on it and they're happy if they can get 4-5 frames per second on high-end CUDA processors. Usually with a static frame of reference and motionless source, convecting the smoke upwards (eg. a cigarette). To put that into Racer, it'd need to simulate the air movement all around the car, on a fine enough grid to look good (probably 0.1m or so), which is a pretty big deal when you consider how large the track is. Though I've seen some work on sub-voxel turbulence before the render pass, so it might be possible to raise that to 0.5m without totally destroying the sense of smoke. Unfortunately I saved all those papers on my laptop which is non-running at the moment.
On the other hand, it would make car aerodynamics easier if we were simulating air movement no need to guess at drag coefficients and wing locations, you could measure directly how much air it's pushing out of its way.
Maybe in another 5 years...
They just need to white out when overlaid, but have a bluey tinge so when they are not so dense they look bluey (as per photos)
Then you could have an array of images to cycle through with some turbid smoke animation, that can play through, but have a different start offset for each particle for randomness.
Or just a better base particle texture, it could have more detail in there and still not look repeaty, imo...
FSR's settings are deffo the right way forward for a smokey look/behaviour, just the actual particle imagery itself that needs tweaking.