As Rich says an air leak will allow unmetered air to enter the cylinders under induction.

To find out if you have an air leak, you could try running the engine with no air filter and then as it's revving high, block the inlet to the throttle body and ICV. This should completely stop any air becoming available to the engine and it should die immediately. I say cover the throttle body, it should be shut tight already when idling, but it could be allowing some air through if the throttle cable is set too tight, so best to eliminate it.

If the engine doesn't die when you do this then you have an air leak somewhere, most likely at the joint between the inlet manifold and head.

If it does die, then either your throttle is not closing fully, your ICV hasn't been initialised or the ICV is not working.

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"Supercharged - 454.1bhp/317.5lb/ft"
Peugeot 306 GTi-6
2000 (X), Moonstone

you didn't say what the original problem was and how you got it running

PAS sensor, try unplugging it and see what happens.

________________________________________

"Supercharged - 454.1bhp/317.5lb/ft"
Peugeot 306 GTi-6
2000 (X), Moonstone

i unplugged the pas this morning was fine for a wile was idleing at about 11oo rpm tho so a little high took it for a quick spin round the block was a bit rough almost wanted to die on me twice, got back on the drive an the revs were going up an down again like before

i am going to try an get a new pas sensor

If unplugging the PAS sensor didn't make a difference then you don't need to buy a new one.

________________________________________

"Supercharged - 454.1bhp/317.5lb/ft"
Peugeot 306 GTi-6
2000 (X), Moonstone