I hav a opel astra classic 2.0 16v idles for a few seconds then cuts off it wont rev at all if I try and rev it cuts off

wasting money changing anything without first having the fault codes read
It is in limp mode so find out why first as it could be a transmission problem that put it in limp mode

Could be a fuel problem/Blockage.
Good Luck

As long as the idle air control valve is working, ( I assume this is what you replaced, I would first check to make sure it is operating correctly), If it is, then Id begin searching for a vacuum leak

Could be plug catalytic conv.

Hi want to know the head talk settings for 2007 1.8 opel astra ecoteck plz

IAC valve problem or intake leak!

Are you sure it is not a spark issue? Some ignition modules have a low speed and a high speed section. If it is fuel, install a fuel pressure gauge you can use while driving to check if fuel pressure is really dropping at 5K rpms. If so, could be bad filter, regulator, or pump.

You may be having a problem with your fuel injection system..

There are sensors that detect if the engine is running after it starts. Oil pressure sensor is a major one. I don't know exactly since I don't have an electrical diagram to see all the possible sensors.

check your throttle position sensor and your maf sensor.