Citroen Berlingo 03reg Van?

I have a really bad flat spot between 2250 and 2750 rpm which i have been told could be my EGR valve... Ive also been told its like a 17mm bolt thats attached onto my exhaust, cannot find it! Can anyone help? It kicks out alot of black smoke as well..

2nd problem is the fuel sender isnt tellin me the truth about how much fuel i have, im having to trip the meter everytime i fuel up and guess when its going to run out, the only time it will tell me what fuel i have is if i go down the motorway with my foot to the floor for about 5 minutes then all of a sudden the fuel gauge will go to where it should be, really weird.!! Took it to the garage and the computer said nothing is wrong, Do i need to drop the tank and change the fuel sender?