I think i used Harimau for these two tracks, I was also using Icarus but kept getting pasted.

On Sebenco, personally I would use the Turbo at the top of the hill going into the tunnel as using it coming out of the tunnel takes good timing which at the time i didn't have. You need to master side shift to get round the track smoothly try not to to take the corners too wide.

On Chengou, Take the hard left, wide and earlier than you think. Also time can be lost on the long sweeping left. Try to keep your nose down right round this part as it will stop you jumping about too much (still learning this myself).