Tim,
The electronics will kill you..... I broke down or had dumb issues... De-activating the abs and DSC will be a massive problem... Stand alone is the only way....... However the e46 325 ITR model can use the stock ECU a lot easier... M52tu= trouble .... I have a garage full of them... Giving a go with the 328 now.. .... If ITR is what you want STOP what you are doing and just go buy an E36 NOW! That will save you $20k.... Not kidding!

Greg