So I installed a dinan cold air intake on my 2005 bmw 330ci, the long tube one that goes all the way down. I know someone who has the exact same one on his 323, and when he revs his engine you can instantly hear the deep sound the intake gives off. Mine only makes a similar sound above 4000rpm while driving. It'll only make a slight air suction sound while I'm driving it below 4000rpm or if I rev it in neutral. I don't think this is normal, I obviously want it to be working 100%. Does anyone know what the issue could be?