Since it's `Frage nach` one would think that it would be `Anfrage nach`. I can't tell you if it's completely incorrect, because historically, it wouldn't have been used this way in the first place. (It would have been )

Still, I wouldn't recommend *nach*, because (following my intuition) the two prepositions 

*Anfragen* in connection with some noun usually comes with [*wegen*](http://german.stackexchange.com/questions/15093/use-of-dative-after-wegen/15106#15106).