I have also Megachip and Agnus 8375 318069-11 NTSC on my A2000.
Agnus is not able to display anything. It's Denise job.
With a Super Denise chip 8373 R4 390433-02, you can be sure that NTSC mode is displayed correctly on PAL TV, because Denise uses RGB lines of the scart connector.
After, you can select your monitor, PAL or NTSC, or adapt a little program to switch.
