i recetly installed DC headers on my scion xb and everything seem to be running well but when I stop at a red light I hear a Humming Noise coming from the engine? Its not really load but it is noticeable. is this normal or did I install something wrong?

 

re trace re inspect your install i dont know what is normal
exaust note or loose components 9 out of 10 times its the instaltion it happens

 

it means the gerbals are running in there wheel!

 

mayb theres a snake under the hood,
the snakes are envading our engines!

 

:oops:

 

i had a loud humming/rattling sound from my engine and some pipe came loose on the firewall.....i just had the dealership fix it

 

No. They're humming because they forgot the words.