M5 Guru (>2000 posts)
Join Date: Nov 2010
Location: Sanborn, NY
Thanked 284 Times in 244 Posts
You will get a lot of different answers for the tuner question. There seems to be a lot of them out there with good results. Some make more conservative tunes than others (especially for "off the shelf [OTS] tunes). I bought my '13 M5 in October, so I'm waiting for winter to pass before I install a tune on mine. I'm leaning towards Bootmod3 (BM3) or OpenFlash. Other common companies like Dinan, ESS, ActiveAutowerks, have OTS tunes. There is a JB4 option as well.
Regarding the downpipes, these are another popular and easy mod. I suggets not paying top dollar as most of them seem to be about the same in quality although some brands tend to fit better. You probably know this already but catless DP's will smell and will require tuning out the emissions codes.
Good luck and keep us posted what you do!
2013 M5 Imperial Blue/Silverstone II, 6MT 50k miles
2000 Anthracite daily driver
UUC dssr and shifter
Supersprint headers with Tubi catback
Dinan 3.45 JED lightened flywheel
282,000 miles and counting
'00 Imola/Imola 104k,
'00 Silverstone/Silverstone 129k (SOLD)