A good set of pistons and rings for you is ONE THAT FITS!
Not being a smart a$$ at all, but you need to measure the cylinder bores and get a match regarding piston/cylinder clearing and ring end-gap. Get this done by someone who knows how!!!
I had a pair of pistons held of at Fastrax Motorsports and sent them my monoblock. From Norway. Oh, and I had normal wear on 2011 pistons and replaced them with stock 2013 pistons.
They checked it out in every way they know, relying on years of experience with polaris CFI motors, and then it was good to go. There is more than one school out there; some say pistons vary in size and others say cylinder bore.
But if you match a pair of pistons to YOUR SPECIFIC MONOBLOCK and have a correct end-gap on your rings, you are more than likely going to see all these trouble free miles that many pro owners report.
From 2013 the reliability issue has pretty much come back to normal (as in no more/less than Cat/Doo). Get a fix kit if you so desire, but check above mentioned things the same way. Better yet, have the supplier of the piston kit, whose reputation is involved, check out your monoblock and set ring end-gap before you even get the kit.
Best of luck and happy riding.
RS