Do you have pictures of the Z banding? You can upload and attach them (might need to use the advanced editor) as a new user. Your use of offsite links is prohibited, but not uploads, as a new user. It's a spam thing, long discussions elsewhere. I did an upgrade to T8-8 on my own over a year ago and it was a significant improvement.
I have the beta (i.e. you print everything but the gears and bearings) geared extruder, and it's been great. Mine is the fixed spacing unadjustable version, beta 2 iirc. The only problem I had was filaflex wrapping around the gears and I never got around to troubleshooting it - Probably trying to print to fast.
PB's QC is erratic...
Modified KickStarter Classic Plus 7/2012
KS Thingybot Delta Pro 10/31/16