The TD5 engine fitted to the Discovery 2 and Defender, is a great engine for tuning. We have been tuning them for years.
The EGR valve bypassis great start in getting the TD5 to respond better, but be careful when removing studs from inlet manifold, if it snaps its a manifold off job.
It is a good idea though to upgrade the hoses to our 5 ply ones, much stronger!
Before tuning takes place we always check for any faults, 
Then if all ok, proceed to tune. 10p td5’s require a physical chip change in the ECU.
Later 15p engines are fitted with the NNN ECU, which are flashable through the OBD port
