Corsa C egr valve

[Qwerty2429]

Hi I was wandering if anyone could help me out, I have a 2002 corsa C 1.7 dti, one problem I've noticed is at first it comes on boost fine but after say 10 miles the orange light with the car and spanner comes on and it stops boosting and feels flat. I think the problem is egr valve but I was wandering if it would be better to either clean it or have a blanking plate put on? If anybody could help me out that would be great

[Defcon5]

Blank it off, then clean all the inlet pipe work that it will have gunked up.