The Dinan intake tube is a 90 degree elbow from the TB. They do this so they can plumb the added/secondary inlet between it and the radiator. The 550i airbox tube extends out at an angle, so some home new solution to get the two to connect would need to happen. I'm actually trying to do the reverse of that at the moment. Trying to run the Dinan airbox with the supercharger inlet plumbing, which is angled for the OEM airbox.

 

The only way you're going to know if you have a good setup is to dyno it so you can see where it drops and climbs and that can be expensive to do this, tweak, re-run, tweak and continue the process over and over.