Razoola, thanks for suggestion.
updating 250 palettes takes more time than expected - i have to disable screen while updating... works very well and it's pal-save!
(re)moving BIOSF_SYSTEM_IO saves some rasterlines but not enough.
with this code it's possible to update all palettes within one frame... this small multicolor-effect runs now with 60fps!

old:

        jsr     WaitVBlank		; wait for the vblank
        jsr     CHUNKY_UPDATE           ; write 125 palettes

new:

swapw1  move.w  REG_LSPCMODE,d1
        lsr.w   #7,d1
        sub.w   #$1e5,d1                ; first black line after chunkyscreen
        bne.s   swapw1			; Wait

        move.b  #0,REG_ENVIDEO          ; disable screen
        jsr     CHUNKY_UPDATE           ; write 250 palette !!!
        move.b  #1,REG_ENVIDEO          ; enable screen

I implemented this update into DIFF.... works very nice, no more tearing ... but I lose some frames because of the wait-loop. I will check this with a timer & trigger!