the complaints but I bet there's a ton of z1 tb's out there working just fine. All I'm saying is you could try them out first. If you hold them up to a light and they don't let any light through(or very little) and you can let them snap shut(springs installed) and they don't get stuck shut they will likely work well. There's also the issues of the shaft seals leaking and the tps not having enough adjustability to meet spec due to bad location of the mounting screws or improperly machined tps key on the shaft...but I don't think Rob's service can address those issues.