Vauxhall Vivaro 1.9 2003 Diesel van cuts out at low speeds ?

Van cuts out while driving!

I’ve got an intermittent fault where the van cuts out while driving and sometimes dose not start there is no faults found on scanner as its a intermittent faulty When i slam the bonnet shout it cuts out i have now found out this is the fuel cut off switch ( Is this met to do that ) could this fuel cut of switch be faulty ?????

When the van is on the motor way it drives like a dream and is ok

NEW PARTS FITTED SO FAR

1) new mass air flow meter
2) new Camshafted sensor
3) new three glow pulgs ( number 4 is stuck in there and rusted also the lead is rusty )

Please help