Generally, running slightly rich will not ruin your catalytic converter but will affect your emissions.
If you are in CA, you are more likely not to pass their
exhaust emission test.
Also, you should have slightly more power.
Try a can of BG-44K, it is a potent injector cleaner which will remove carbon deposits. Our BMW dealer carries it. You should be abel to find it at certain shops but is generally not available at automotive stores. UIt is generally sold to mechanics. The cost is about $14.