hi, some mods :
Diezel mod:

C35 : remove
C34 .047uF
C25 : remove
these three mods remove harsh 

C42 1uf
D3 DEL
D4 1n4001 
------ make the sound more dynamic and full
C36 .1uf----- EQ more usefull

Boogie/Bogner mod:

C35 a enlever
C34 .047uF
C36 1uF
D3 led
D4 1n4001

EN PLUS:
R46 increase values, more pre-distortion + mids
R41 reduce value you obtain more distortion (470ohms to start)


Mods don't have the same sound of diezel amp or Bogner amp, but it can be better tant the stock sound.



Keeley mod:

C20 .22uf
c42 .1uf
c37 , c39 , c17 , c11 1uf
c8 .22uf
c9 .1uf
c20 .22uf
d3 , d4 LED