[Dan 3222's]

If it is a faulty N75 valve then it won't be cured with a remap. In fact you had better put a new one on before the remap!!

I had similar noise a few times but since I cleaned up the EGR I haven't had it again. My guess with mine was that it was sticking open when switching off allowing exhaust gasses to pressurise the intake side when it shouldn't be pressurised. Was noisy through the air filter housing. But that is just a guess for mine.