ive wanted to do this for a while, it only works this easy if you have a 525i m50 tu to start with, like I do. Doesnt the s52 rev to like 8k rpm?? our tach would be maxed. You dont even need to tap another coolant temp sensor either, there is a harness made that splits the signal from the one. Use the headers from your m50 or weld up the passages on the obd2 headers and get some 02 sensor plugs and youll be good to go. use your intake too, everything thats on your car now but the s52 longblock and the chip should do it.