To be technical about this, diesels don't have such a big
problem with back pressure when lifting off the throttle.
Petrol engines have a butterfly that controls the amount of air going into the engine, this is moved via either a cable (older cars) or a motor (modern cars), when you lift off the throttle, the turbo is still compressing the air but because the throttle body is shut the air can't escape and applies back pressure to the turbo, a dump valve does as it's named, dumps the compressed air to either atmosphere or recirculates it the when the throttle is lifted.
Deisels sound ****ing gash with a dump valve lol!