CEL at 3000rpm or just above

my cel light comes on at approx 3000rpm or just above, (octavia 1.9 '04). The next day the light has sometimes gone but not always, But as soon as I hit the 3000rpm mark its back. Any ideas?. A garage thinks it is to do with the egr valve, which they have now cleaned out twice. Now thinking about adding a catch can and delete pipe.

Edited 13 May, 201016 yr by kingcarp69