Hi there,
Just wondering, have you considered software? like the BMS JB4 which is the best bang for buck in my opinion. I had it on my 320i without additional mods with very good results for almost 4 years, no issues what soever. I still have mine for sale if you're interested... took it of when I traded. Also, very easy to remove before services, never traced while on MP.
Let me know if you're interested.
SV