BHA, BHT, ethoxyquin are things to avoid in pet foods.
Go to
www.dogfoodanalysis.com and you'll be able to look through different foods. Generally, 4 & 5 star foods are recommended for yorkies
If you look through the 1, 2, and 3 star foods, and click on the individual foods in those categories and read some of the reviews, you'll be able to see the ingredients that are not recommended.