Heres a bit more info about the Tech 1 and its cartridges.Theres different tech 1 cartridges for each model commodore,the VP ECU actually uses the VN ECU cartridge,which is called holden's 1988 ECU cartridge,this cartridge also does holden astra, holden camira, VL group A commodore,as well as VN and VP V6 and V8 commodores.The VP cartridge is actually only for the BCM (Body Control Module),which was first used on high end (calais etc) VP models..these have a seperate ALDL connector in the fuse box under the steering column just for the BCM.Theres also two VR and two VS cartridges,one is a dealer service cartridge,the other is a systems cartridge.The systems cartridges dont have the security stuff included on them,which is used to access security info like the radio pin number or key numbers etc, also to reprogram the central locking,you can set the central locking on VR/VS so that all 4 doors open at once with one press of the button on the ignition key,or you can program it so that just the drivers door unlocks with the first press,then if you press it a second time,or hold the button in for a second or two,the other doors will then unlock too.You can also program new key fobs with the dealer service cartridge.You can only add an extra ignition key though if you dont have the security code thats unique to your vehicle.Holden can access this security code via TIS2WEB or TIS2000 by using your VIN.Ive heard some dealers wont give out this code,but there are some about that will though,I got mine way before I even got a tech 1,I got a new key programmed one day,and the guy used my VIN to get this code,I just asked him for the bit of paper he wrote it on when he was finished,and he just gave it to me..This code lets you add a complete new key if one gets stolen or lost.Once this new key proceedure has been done,the old key will no longer start the car,whereas if you just add an extra key,the old keys can still open and start the car.So if the keys have been lost ,then its best to get this code and program it from scratch. Theres also a interface module available so the tech 1 can communicate with OBD11 vehicles.It only lets you do basic diagnostic stuff on OBD11 equipped vehicles though,like error code checking or resetting and basic engine sensor reading etc...You also need the global OBD11 cartridge as well for this to work along with the interface module.The Tech 2 was used from the VT onwards.I was looking at a dealers TIS2WEB and theres actually tech 2 menus on it for VS,the service manager reckons that the 1996 and later VS's cant be read with a tech 1 and you need the tech 2 instead.Im gonna get a tech 2 in the next few months,it should be an interesting bit of kit.It does a hell of a lot more than the tech 1 does,like accessing the dash for programming etc.(the tech 1 also has this capability,but was never used in this way on aussie cars,only over in ther USA)..Buying a tech 2 is a bit of a risky buisness.Theres some around on ebay that arent a proper vetronix tech2,but they still want the $2000 or whatever for them.They are OPC brand and are called a tech 2 "flash".These units look exactly the same,but are a cheap ripoff of the proper thing.Apparently they cant be updated or something along those lines,and apparently cant even do all the things a proper tech 2 can do.I wonder how many people have been ripped buying one of these units.Also the early hewlett-packard tech2 units are some of the first tech 2's to be made.The parts for these units are no longer available,but if you can find the parts you need ,they cost heaps to fix .The bosch/vetronix tech 2 is the best one to get.They go for around $2000 second hand.Brand new they are around $4000 or more for a pro version of the kit.Even the tech 2 is just about obsolete now,it cant even read CAN diagnostic systems natively,it needs an interface module called a CANdi module or Controller Area Network diagnostic interface.These interface modules cost around $200-$400.The hardest part though,just like the tech1 ,is getting the software for aussie vehicles.In the USA they did away with using single cartridges for each car,(although they were still available if dealers requested them),and introduced a special cartridge called an MSC or Mass Storage Cartridge.These held the equivalent of 10 or so single cartridges and could be updated online like the tech2 can.This system was not used in australia,they only had single cartridges available here,and the dealers never had the gear to connect the older tech 1's to a computer anyway.The first tech1's had to use a special adaptor cartridge with a serial port in it, so you could connect the tech 1 to another computer.The later version of the machine called the tech 1A, had the serial port built into the side of the machine itself,so it didnt need the special cartridge to connect to another computer.Its a shame the aussie stuff was never made available for download to a MSC.It would have made things a lot easier and cheaper.Im actually working on a way to get all the aussie cartridge software copied over to a MSC.Then you just need the one cartridge to do VN-VS.Hopefully I can work it out one day .