I believe 70k is still not that high. My family owns an X70 with 120k+ KM mileage. It is still running smooth like new (albeit we just made a claim for a new gearbox). Retain your warranty and talk to your service advisor if you feel your car not performing as it should.

No doubt walnut blasting has been done a long time. But modern engines very rare carbon build up badly (less than 100k mileage la, I can be wrong). Unless you skip or delay oil changes and lenjan the car everyday, then maybe.

Is your car jerking? Or significant performance drop?