This may not help many people but for what it is worth here goes , my X & Y toothed pulleys were slightly eccentric . I went to my local bearing stockists and purchased new ones (4 off , 2 for later mod ) . These are machined to the correct profile but do not have a hole through the boss so it was necessary to mount them in the lathe using a d.t.i. to get them concentric and then bore and ream the hole to 5mm . They have made a real improvement in print quality . I believe the originals are an extrusion to a not very accurate profile .
Another solution is to install GT2 pulleys and belts and you get an even better improvement. That said I’ve had almost perfect results with the eccentric pulleys. It depends on the way you tighten them. But I have to admit it’s not so easy to achieve and you can’t be sure it will last much.
Thanks mine is working well now but I realise not many users will have the needed equipment to do what I,'ve done .