Blow off valves

Just to clear things up a little for the non technical type!
"A good blow off valve is an absolute necessity for high performance turbo systems. A well-engineered blow off valve prevents turbine damage by quickly relieving excess boost pressure without sacrificing boost response. Conventional blow off valve designs require choosing between flow capacity and boost response - blow off valves with high flow capacity generally have poor boost response, while blow off valves with good boost response are not able to handle high flow capacity" (as taken from Apexi blow off valves: