Freelander 1 TD4 a new whine noise

My 2001 TD4 130,000 miles with new auto-box fitted at 86,000 Full Servicing still done I do love this car

Not long ago had the main pulley wheel and drive-belt replaced (the one that drives the AirCon compressor)

Been happy as Larry, but just started is a new whining noise, it only comes when I apply and throttle and the whine rises and lowers in pitch with engine speed and gear changes. Stops the minute I close the throttle (no whine on coasting).

Describing this noise, it sounds like the supercharger drives on the big American muscle cars! A sort of belt-noise whine...not really annoying, but it wasn't there before...

Would like to nail it before it fails. Any ideas what this is most likely to be? ,

As ever, I do appreciate the advice here.

Aux belt tensioner pulley? Prime suspect when other pulley's are replaced - I think the bearings are made of chocolate.

PQG100340L - If you slacken the upper bolt 1/4 turn, then loosen the lower bolt and take all tension off, you'll be able to spin the pulley and see if you get that "zizzz" noise.

Many thanks - I need ramps, will check when I get them.