Sounds like your GLA45 has what is called here in the US 'AMG Sport Exhaust' which does have a solenoid activated valve (2015 MY tied to 'S' and 'M' mode and 2016 separate switch to turn on/off valve).
Yes they are here they are the altternative for the Q3 for merc lovers. I have frind that has one and after I sold my 2014 Q5 S-Line he sent me to the locale MB dealer and from there it's all history (I was looking for a sport car that can replace my cbr600rr and could allso crouse lite filds).
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