Germany is real strict with vehicle inspections... I did two tours there and both times when I shipped my car, they caught something wrong, to include, under carriage dirt
I had a Honda Civic with the folgers can and all and it failed...luckly the exhaust I had you could order silencers for then and thats what I did.
I know you got the ATAK, .... maybe you might want to get some quieter mufflers... as for silencers that will fit that system, I wish I had an answer for ya.
Oh and have a good ol German bier for me and a brat w/ kraut