brake pedal,Could the brake servo booster that the master cylinder attaches to cause the brake pedal’s excessive travel?

I have a Toyota avensis 2008 model. My issue is the brake pedal is traveling to the floor when brakes are applied. I have inspected the brake lines, calipers and have changed the master cylinder. But the problem has not gone. The only other option am remaining with is the brake servo booster that the master cylinder is attached to. When I step on the brake pedal a sound like of some pressure being released comes. Could this servo booster be the issue?

My car has 150000 miles.
My car has an automatic transmission.