How quick we're PE to send it back do you know?I sent mine to PE for a service it's free if under a year old ,otherwise its £30.
I had a DART kit fitted FOC at the same time as I didn't fancy digging around in its guts,great service and set up from PE.
DART makes it quiter and smoother,haven't really noticed any efficiency changes but I haven't tested it,as I top it up as soon as its low.