hey i was just wondering if the plug and play tuning boxes are any good? ive been quoted £450 for an ecu chip upgrade on my 05 plate 320 d, (e90-91) to take it from 163 to approx 200 bhp, and upto approx 400 lbs torque, obviously the tuning boxes are cheaper, but are they as good? do they alter the fuelling , boost, timing? does it make the car smoke loads? any help would be great people thanks, wayne.