Dino

I'am the proud owner of a Toyota VX Landcruiser and as I planned to tow a large caravan around Australia I decided to have a GVM (Gross Vehicle Mass) suspension upgrade but the problem I have now experienced is 20mm sag in the suspension on the drivers side. The GVM upgrader & the Toyota dealer who had my vehicle for two days apiece were unable to solve the problem, so my question is, has anybody else experienced this problem & what was done to fix it ? Please help, Dino.