I don't know much about Peruvians, but check this out: http://riobravoreptiles.com/boas_peruvian.htm

Also, you don't have to feed adult boas every week. I feed my adult girl one jumbo rat every three weeks (normally feed the babies every week).

Check out the muscle structure and the tail. Boas typically have a more "boxy" appearance that BPs, which appear more round. But a healthy boa will have a nice round fat tail. If the tail is skinny, the snake isn't being fed well.