I am not aware that MS installed filters. I am still trying to find a way to install a new larger vent and think I have it by going fwd under bed to bow by anchor locker.
I have solved the odor problem on my MS 34HT w a DIY bubbling system.
For info see Bacchus link and scroll thru Projects.
Happy to answer any questions.
2008 MS 34 HT Trawler