To me, it only reminds of "
I Think I'm Paranoid" (Garbage).
If I had it I don't think I would notice. Listening repeatedly I can say it sounds like "nothing special" at most: let it take another 50000 km. to develop into anything indicative.
Why don't you add some firewood accelerating? If it were a mechanical fault it should get more explicit (or finally break down to discover
), probably. If it just vanishes in the noise otherwise - enjoy!