Mk7 tourneo black smoke

[lewgiboy]

Good evening to all, im after a little bit of help if any one can.
I had a look at a 56plate tourneo with black smoke when you rev it now in my mind thinking egr now if i disconnect egr rev it to see if still there or not..
Now if i do will it leave engine management light on or other problems for the seller if i do walk away ?
Thank you any help much appreciated
Or is there any other way to check this without tampering to much it only happens when you floor it