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

MBTN, KCSP, IDRR, ?, EFPV

GEQT

Explanation:

MBTN, KCSP, IDRR, ?, EFPV

The logic followed here is :

M → (-2) → K → (-2) → I → (-2) → G → (-2) → E

B → (+1) → C → (+1) → D → (+1) → E → (+1) → F

T → (-1) → S → (-1) → R → (-1) → Q → (-1) → P

N → (+2) → P → (+2) → R → (+2) → T → (+2) → V

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