Hello.Could someone explain simply and clearly,how a dodgy exhaust can affect engine performance?I understand the problem with noise etc,but what im not sure about is when i put my foot down,there is a minimal response from the engine,just revs higher then eventually picks up.Does the engine need some kind of back pressure?,which the exhaust provides?Im only asking as i dont want to fork out the pounds,if this is going to get serious.Ive taken it down to kwik fit and they have said my back box is blowing,and this would give me the problems with acceleration.Please explain for me,so i can then explain it to her indoors....cheers