Over the last couple of days I have noticed a slightly different noise from the engine compartment - hard to describe, but sounds slightly rough - almost like a resonance / buzzing / vibration. This is not loud, but I can notice it.

In the mornings I encounter a nightmare of a roundabout which only ever presents small gaps in the traffic. Im not sure, but the change in noise may have started after I hit the rev limiter in 1st when pulling out. (first gear is way too short in my opinion)

The car is a 1.9 PD - 55 plate with 33K on it.

Any ideas what it could be?

Cheers,

Plastic cover around your airbox always rattles around that rev range, have you checked to see if there is any wear on it showing it could be loose?