So, just for arguments sake, if the EWS is tied to the key, how people get new keys for their e46 and program the keys themselves without
changing the ignition lock cylinder?
Okay, I talked to a friend in South Bay who's been tinkering with the DME. He said that the key and ignition lock core can be reprogrammed through the EWS module. He's not sure how to do it himself yet, but it can be done. Whether or not its worth it will depend on the price.
So, where we're at is that it IS possible, in theory, to hook up an MS43 to the M52TU wiring harness with some manipulation. I think as soon as we verify all of the sensors, servos, solenoids, and motors attached to the MS42 are the same as the ones attached to the MS43 then all thats left is to try it out!
Okay, I decided to help out Hornung418 a bit a sift through the part numbers on realoem.com. I came across something interesting about the "Suction Jet Pump". It looks like its referring to the fuel pump, but whatever it is, its located in the fuel delivery unit at the tank: Sucking Jet Pump Valve
Also, I noticed that the secondary air pump already has a pin assigned to it on Module 4 pin 3. For the Module 4 connection, both the MS42 and MS43 already match up so no modifications need to be made. But for some reason theres a second connector going to the secondary air pump on module 3 pin 52, which the MS43 requires. wtf...
I figured out what the Suction Jet Pump Valve is and what it does. Its for the brake booster. Heres a description of what it does: Suction Jet Pump Valve Description
. The description says that this part was only used on the MS42 DME so it looks like we can just remove it. That saves us another step and makes the MS43 more compatible! Yay!