In on a lean situation I will see grey/white. But not a build up where it drops out. My etec runs around 16-18 on the afr gauge down the trail. Basically anything less than 40% throttle opening. When running down the trail with a extremely rich tune closer to 12-13.5, runs like garbage, i do not see it at all.
keep in mind, my boost setup differs from many conventional etec s in that all my fueling is controlled by the stock injectors. No secondary injectors. With that said, av gas has not hurt the stock etec system, running a set of secondary injectors you may see different things.
I've always wondered this too, but I don't see that being good for things, especially a turbo.Do you need to run wide open then cut the ignition to get a good plug read?