Saw your youtube clips and enjoyed. :).
I have a 1.6 vw Golf 2007 petrol and my idle is not so smooth. It shakes a little every now and then. I recently replaced the sparks because was running in 3 cylinders. The problem was on no. 4 - the spark was black and a little wet. Now I took off the sparks for a compression test and guess what? The no. 4 was black again. (the compression test went well). What do you think the problem could be? The no. 4 injector cloged?