Supra throttle linkage is kind wimpy (adequate at best). I also would like to know.
I haven't ever seen any upgraded throttle linkage specifically designed for the MkIII, but I've only had mine for 3.5 years so I don't know as much as some of the guys here who've been at this for a lot longer. Could be I just haven't seen whatever upgrade may be out there. Maybe something can be adapted. Sombody has probably done an upgrade in this area.