On your linkages be sure when you take them apart get some penetrating oil and spray each of the threaded ends, with a metal brush work the oil into the threads and work the adjusting nut so each of your links can be easily adjusted. When reassembling - snug up all your joints (including the firewall to the throttle pedal) so get as much slop out as you can. That is about all you can do to clean up and re-work the adjustments from the pedal to the carb. With all the adjustments and ball links - that is how the slop gets developed - all Z's have throttle surge due to the linkages (or at least 99 out of 100). It's been a problem since the original design. The throttle cable is a complete correction - one cable from the pedal to the carb - best of luck with your project.