I get feeling guilty about it, as it is a lot of money to spend. I justify it somewhat by keeping my cars a long time. We have 4 BMW's in our family, with the oldest a 2000 540/6. It has 275,000 miles. The X5, 180,000, etc...And my passion for BMW's has carried on to my son, and that is quality time we get to spend together. So yes, cars are our hobby as well.
Not sure how to id the tune or remove it, but someone else here can chime in perhaps. Keep in mind that if you delete the tune, the CEL will come on because of the catless downpipes. I know you mentioned buying a set of OEM cats, every once in a while the Classified section here has some.
Battery....get the
BimmerLink App and a
VeePeak. With these two you can register the battery. QSilver has a great description
here. One other thought, you can take the battery to any auto part store and have them test it.
Let's see some profile photos.
L