Oh yeah excatly! For real, I'm 54 and my thinking has been from my past experience with old cars and is all wrong. This is actually the first car I've worked on with fuel injection. I was driving a friend's car home from work today and it started to dawn on me exactly what your saying. I was just getting an idea of the ECU detecting a problem then actually turning off the cylinder. So stupid. Now I feel sort of panic and like I'm in over my head. The X5 is or was my daily driver. I had just finished 3 new CV joints and bearings and put in new drive shaft about a month ago. And had just bought ball joints and other stuff to rebuild front end when she started crapping out, then all the other stuff. So about 3000 in three months. I know it's a sob story. I have my friends car for 5 more days. The compression tester is here tomorrow so I might as well follow through with that. I'm thinking of throwing in towel and try and sell it for 500 bucks, try and return the front end parts. Damn it's frustrating.