"Chirping" v6 - I'm stumped

[Robson Rover Repair]

OK folks, here's an unusual one which might be simple but I'd like people's opinions.

The v6 has began to "chirp" from around 2300rpm onwards regardless if warm or cold.

At first I thought it was a pulley as it chirps more when the revs rise but oddly the throttle has began sticking also around 2300rpm also.

What sometimes happens when she idols for maybe 20 seconds or so there will be a rattling from behind the throttle body or close to it.

My vis motors are fine, inlet manifold is grand also.

So my only thoughts are air idol control valve perhaps?