This car problem is getting beyond a joke. It's a 1999 Vauxhall Astra 1.7 turbo diesel and the engine management light keeps coming on with power loss. It's been on the computer (Code PO400) and had the EGR unit replaced. It worked perfectly for a couple of months then the engine management light started coming on again randomly. On the computer again and same code came up. The valve was cleaned (on 2 occassions) as it was full of muck but the light still randomly comes on with loss of power. Why is the valve getting clogged and why no improvement when its cleaned ? Any ideas of what is causing the problem and any solutions. please?