Exhaust various

Hi guys
Noise from engine on cold like a fan spinning then stops also seems to cause exhaust vibtartions (to me any way)
Second when revving in neutral slighly stock muffs by the way as the rpm lowers I seem to get popping or a sucking type noise on de acceleration ?
Is there a hole and how to test
Much appreciated
Noise from engine on cold like a fan spinning then stops also seems to cause exhaust vibtartions (to me any way)
Second when revving in neutral slighly stock muffs by the way as the rpm lowers I seem to get popping or a sucking type noise on de acceleration ?
Is there a hole and how to test
Much appreciated