International B, GT Kart Championship 125.
I had some trouble with the first two bunches of Kart races. The second one in particular was very difficult for me: I simply had not level of skill demanded, the powers of concentration, the abilities, the quick responses. Only after maybe 150 restarts I finally nailed the last race after some desperate moments which almost made me trash the entire game.
Now, this wouldn't matter too much if we didn't have to win every single race in order to progress to the next level, and I am a career animal pure and simple.
On the National B level I therefore went straight to the Kart 125 races, to see whether it served any purpose to continue, and I found what I had feared: the Silverstone race was easily won, but the two others are way beyond my abilities. And fiddling with the transmission helps somewhat, but I still spin off the track with boring regularity.
I have had little trouble with other races, nothing more than makes them interesting and fun, nothing too different compared to GT 5, but for me the sudden jump in the skill level demanded by the Kart races is so vast that I cannot bridge it.
It's called "Boss Fights". There's a sudden jump in in-game level of difficulty which have ruined many an otherwise excellent game for me. I shall never be able to finish Doom 3 or Dead Space 1 and 2 on more than mediocre levels. It's a nasty and unexpected surprise that I seem to be unable to finish GT 6 at all.