I don't think it's so much a matter of "preload" as it is that this is a variable length actuator and if all the slack isn't taken out when you install, there is free play for the wastegate to open slightly and not hold pressure. There are minor differences in every turbo, that's why the rod is threaded. If it's even a hair longer than necessary, it won't hold the wastegate closed. They can't make it exact because there's no way of knowing. A turbo is far from an entry level type installation. If you're not prepared to do a little thinking and work, maybe it's not a job for you. Lots of stuff comes without instructions, why do you assume everyone and everything has to coddle to the amature?
Sent from my SM-G930W8 using Tapatalk