Here is the reply back from Einszett USA
"There shouldn’t be any issues with applying this on an E90. It has
been applied on the entire range of BMWs.
If directions are followed exactly, the owner should have the setting on
fresh air, direct air setting (not footwell, defrost modes). When inserting
the tube it may take a few attempts to get it in smoothly without hitting
anything. Once they insert it all the way in, they can begin application.
They can check out the following link for more help:
If the user is having any issues and doesn't feel like they're doing it
correctly, they should have a certified mechanic apply it for them."
If you have any other questions please let me know.
Greg @ DI