IMO it looks like it could very well be a Torx plus . . . using a regular Torx socket might remove the bolt, but internally round it, making it that much more difficult to remove the next time
Nevertheless, since it doesn’t seem to budge . . .
Use a 3/8" drive impact driver, in conjunction with a hammer and the appropriate sized socket
I wouldn’t be at all surprised if that will shock the bolt loose, and after that you’ll be able to remove it
BTW . . . why do you want to remove the throttle body entirely, just to clean it
I’ve had good luck cleaning numerous throttle bodies, WITHOUT removing them to clean on the bench
Another thing . . . on several cars out there, you have to use a pro-level scan tool to tell the pcm to relearn the throttle body after such a cleaning. On some cars you’ll get away without doing this. On some others, if you don’t do this, the idle will be erratic, too high, too low, etc. until you perform this step. On yet some others, the idle will be a mess until you drive the vehicle, under various conditions. But others will never “figure it out” on their own
On some of the older Benzes, the throttle body end stops will be relearned every time you turn the ignition to position 2, without starting
I’m not sure if BMW is the same way, though
I just thought I’d warn you of a possible future problem