Yes, I have gotten lean burn to work, and it helps quite a bit. You can cheack my fuel logs to see the benefit.
The vacuum leak thing helped by fooling the pcm into thinking that less air was passing by, and therefore it would be in a lighter load part of the ignition maps, meaning slightly more advance. I would say this will not work with all cars because this vacuum leak was unique in that it is a vacuum booster valve used for the the power brake booster, not a "true" vacuum leak. With lean burn, I no longer use the vacuum leak.
I've never checked the plugs, not worried about the color
