Forget what the gauge is called, just know that it sets your downstops.
Set your DROOP by measuring from a fixed point at the front and rear of the chassis with a ruler.
Simply set the car up ready to race, sit the ruler against the front bumber and from a set point, as you lift the chassis until just before the point the tyres leave the ground, measure the difference between the resting mark and the lifted mark. Basically, if you are wanting to set 6mm droop, you need to lift 6mm before the tyres leave the ground.
Do this front and rear, then use the droop/downstop gauge to set the downstop points. You should have to move the srew too much to set both side and each end, this setting will ensure that no swing arm will travel lower than the other.
Look at it like this.
Downstop = same down travel of each swing arm, ie: they will stop at the same point on each side of the car
Droop, the amount of vertical travel in your suspension before full load. ie: you chassis will lean to one side, therefore if you have enough droop, th inside tyre will remain in contact with th ground giving you more traction, however too much droop and your car will be slow to respond to direction changes.
Obviouisly there is other settings that will effect these two, so I suggest you go here http://www.teamxray.com/teamxray/pro...ria=0&catName=
This is a great tool and will help you understand most of the settings required in racing touring cars.
Hope it helps
Sorry, should have told you that when you get to thie above site, download the T2 set up book, 43 pages of racing knowledge