Whir at 1000rpm

Hopefully somebody can help.
I have a 2000 jimny with G13bb engine.
Once it has warmed up the idle drop to around a steady 800rpm ish.
If held at 1000rpm you get a little whir from the engine.
Only appears at 1000rpm and goes away at idle.
Only noticed it as if revved the it first stops at 1000rpm for a few seconds then drop to 800rpm.
I have removed the Power Steering belt and the fan/alternator belt and ran for a few seconds but it still remains so it rules out any ancillary so definitely an engine noise.
Also changed the oil and filter but no change.
Can anybody shed some light

Thanks James

Is your truck modified ?
Always helps to give as much info as you can
To be honest you will stand a much better chance of figuring out the problem than we will guessing what it could be
Wheel bearing or tyres would be my guess

Not modified completely standard.
This is at a standstill.
I wouldn't drive down the road without a working waterpump!

Dipped the clutch ? Could be the release bearing

Tried that, there is a slight noise from the thrust bearing but not the main noise.

Hmm
Not many more moving parts to go at , have you tried a mechanics Stethoscope to try and pin point the source of the noise