need a good non-dealership Lexus mechanic near the Granada Hills, CA 91344 area - please help

This is actually easier than you might think;

1. Find the local number for AAA (American Automobile Assn)
2. Call them & ask them to refer you to an independent garage specializing in foreign or Japanese import cars. They will ask for your zip code and then give you at least 1 or more nearest you. This service is free, you needn't be a member.
3. Armed w/the information from #2 above, call each of them and ask if they are a member of the Better Business Bureau (BBB). If you find one who is, ask if they service Lexus. You've just found your mechanic.