most ecu after 98 were soldered! so you need to put a socket in the board,then chip either to full fat or +10 or less smoke +5 and not far off its your choice on these,
small jobs worth doing,
backbox removal its rather heavy for what it does and gas escapes better withlittle or no
extra noise worth mentionning
blank egr as you say some say it worth removing the plastic iintake and throttle body and replacing with a straight piece of pipe,
can also fit manual switch to intercooler, as stupid vauxhall only have it come on with main fans,very rare,it makes a difference as intake temps can come down by as much as 30degree,s!!
carefully very carefully,a quarter of a turn a time,on the wastegate arm, till you are happy when you have chipped it, this will lessen smoke, and give a fair bit more poke until the wastegate catches up with itself, but its worthwhile doing,change gear at around 4k and it dont very often catch up
oil change every 3 k with good quality oil makes a difference, as does running on super diesel,
mine would easily light up the tyres in third, so had to back it off a bit for the mrs,