Which letter-cluster will replace the question mark (?) to complete the given series?

PYWB, MVYD, ?, GPCH, DMEJ

JSAF

Explanation:

PYWB, MVYD, ?, GPCH, DMEJ

The logic followed here is :

P → (-3) → M → (-3) → J → (-3) → G → (-3) → D

Y → (-3) → V → (-3) → S → (-3) → P → (-3) → M 

W → (+2) → Y → (+2) → A → (+2) → C → (+2) → E

B → (+2) → D → (+2) → F → (+2) → H → (+2) → J

So, the letter-cluster that replaces the (?) to complete the series is "JSAF"