HI have you checked out all turbo pipes,i fitted a non genuine lift pump to a 200tdi the other day and it did not lift enough fuel up as the arm was bent at an incorrect angle,its just an idea to check out,most of the time a 300 will rev alright to about 3k then run out of power due to fuel starvation oh yes also check your fuel cap as these have caused a vacuum in tank as they are not breathing properly,are all fuel lines clear with no blockages hope some of this helps,tiga