Why is the rum gone?
Join Date: May 2012
Location: United Kingdom
County: Greater Manchester
How often is 'quite regularly'?
Mine regened every 300 miles or so when the DPF was end of life.
The increase in performance 'might' be a sign that your car is running lean in normal operation, As the regen chucks more fuel in (albeit during the exhaust stroke, it will still result in some extra fueling for the compression stroke)
the turbo will be quieter as it's doing less during a regen, if you take your foot off the gas pedal the turbo spools down completely.
Running lean is either because there is not enough fuel or too much air.
First thing I'd try is reset the ECU, (disconnect battery for 20 mins)
then check injector correction values and flow rates (IIRC MES tells you both these figures)
(could be a knackered injector or two)
Or there might not actually be anything wrong (just realised the first thing I thought was, it might be broken, but re-reading your post it occurs that it might just be the way your car is?)
My 1.9 got louder when regenning, but I never noticed an increase in performance, but like you say I could definatly tell when it was doing one, not just because of the fuel consumption.