I've seen it, you've set a great guide there, really nice!
But the transversal stutters are frametime spikes when the UE4 engine loads the next tile of the track...
Most of time it's barely noticeable, but since I've managed to get it running almost perfectly, might aswell hope for 100% smooth.
Using VSYNC never worked flawlessly for me, even with the profile inspector settings and the .ini file framelimit. I fixed it with RTSS ScanlineSync along its Frame limiter(6 decimal digits precision). It eliminates the usual stutters and reduces the transversal ones quite a bit.
PLUS lower input lag.
By the way, without the performance issues, the game is for me a straight up 10 out of 10.