I have 535xi with Procede V5 with dual intake. I want to get 535XI downpipe but seems its hard to find since the demographic is so low for this particular vehicle.

Can I run with just chip intake and downpipe and get a nice horsepower gain. I would not prefer to put a loud exhaust on this car, I like it fast and quiet. Any where I can get a catless downpipe for my car? HOW MUCH? Thanks