My baby threw up when I first brought him home but he never had diarrhea. The vet did tell me I could give him 5 cc's of Karo syrup to help keep Reggie from becoming hypoglycemic. I also have given him plain chicken or turkey baby food in small quantities when his tummy was upset. Cottage cheese is another favorite of Yorkies... in small quantities when his tummy is upset.
Check with other members first to see what things to avoid if he has diarrhea though since I haven't had any experience with that.
Hugs and prayers for you and your new baby.