I used it also a few weeks back. First I used it on my commercial lawn tracktors and it smoothed them right up. Next was the bimmer. Not alot of smoke came out but some black water started to exit the muffler. Not like when normal condensation comes out. Next day I got the light. Checked the codes and its the lean bank 1 and 2. My bmw tech said maybe the o2 sensors or a vaccum leak but to change the o2's first. Wonder if the seafoam fouled them with the carbon deposits it removed.