Can excessive carbon build up or an over rich tuning result in a valve tick? Checked my valve lash and all of them are in spec. Should I take the car to the freeway and give a good thrashing to clear the carbon? I don't drive hard often.

 

Bump

 

sure it's not the injectors you are hearing?

 

Definitely sure. It happens loud. But only between 3000 to 3500rpm. I'm sure its not a rod knock, but I'm not sure if excess carbon build up in the head can cause this?