Hey guys from down under! No 540 here unfortunately had to put her in storage. I will be here for a the foreseeable future.
Thanks for the comments the build took forever but she is a dream! I did install the headers and they are a PITA to do took me like 12-15 hours the first time. It is much easier to pull the motor. 5-7 sounds far too optimistic to me. They are an incredible addition though! I can not say about the tune but I am sure it would be fine... I would add an AFR when you do it just to be on the safe side. My tune was fully custom and like said I had a piggy back module to make live tuning possible... We also had sooooo much trouble with the MAF remapping.
A good tune should be able to compensate at any temp!! That is the point of the sensors and fuel injection!
2001 540i - Orient Blue
M5 bumpers, wheels, mirrors
S/C, water/air IC
A1 Headers, Random Technology Cats, Eissenmann Exhaust
3.15 diff, evosport power pullies
Koni Sports, Eibach Springs/Sway Bars