Howdy again!

Recent I was doing some modifications to my BA XR6.
I changed the K&N Panel filter in the air box for a Pod that I attached to a peice of intercooler piping and fixed in with a hose clamp (inside the air box).
This was mainly for the induction noise, which worked awesomely.

Then I suppose about a week down the track it developed a vibration under accelleration, coming from the engine bay.
Only while moving (stationary revving was normal), and only between about 2500 and 3500 rpm.
It sounds like a metal buzzing vibration noise.
It's hard to explain.

Anyway, I removed the Pod and put the panel back in.
It made a difference, the vibration now does still occur (but not as audible) except at one certain rev while moving, (which is about 3000rpm, but then at say 3100 it goes away again).

I also replaced the intake snorkel with an XR6T one but I doubt that is making the noises I am describing.

I tried replacing the PCV Valve, which is when the noise started, but I have since switched back to the old plastic kind, and the noise remained.

Any ideas?

Thanks