There's a vocal part on Santa Ana Winds that I always thought was Brian until I was told it's actually Carl, which disappointed me. Funny, it's like we're trying to spot the Yeti, isn't it? "Look! It's Brian! On there!!!" We just want to have him on there, do we?
There is a vocal part - a whole one second - where I think it's Brian. At the 2:37 mark, it sounds like Brian singing "oh the". He may be buried in the harmonies somewhere, too. Who knows...
Brian's definitely there near the end of "Santa Ana Winds", doing a little "oh oh" or "whoa oh" bit. You can hear it more clearly on the "alternate" early version, from which elements were used for the eventual official version from KTSA.