Not sure what the DP chip is but there is a firm in the u.k called superchips and lets just say the job they do in re-mapping the ecu has made a great difference, got a 3.0d 2004 e53 and it does move very well, considering they wiegh over 2 tonnes it is amazing. As long as you perform regular oil changes and use good quality stuff, then the engine should be able to tolerate the strain on it (superchips say they do extensive tests- I am sure they can jack up the bhp even more but would run risk of melting down engines!)

On a different note, does anyone know what colour coolant the diesels need?and if I can't go to bmw, is there any off the shelf stuff (mobil/texaco/esso that can actually be mixed safely with the orginal coolant in the car?just for top up purpsoses off course.