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

EGJM, GFLN, IENO, ?, MCRQ

KDPP

     E    G   J     M

     5    7   10   13

     G    F    L    N

     7    6   12   14

     I     E    N     O

     9    5   14    15

    +2  -1  +2   +1

=   11   4    16   16

     K     D    P    P

     M    C    R    Q

     13   3    18   17

2 is added to the first letter, 1 is subtracted from the second letter, 2 is added to the third letter and 1 is added to the fourth letter.