I removed the airbox snorkel and opened up the top.
After much experimenting, including initially making up my own needle from and old FCR needle I had lying about, I got a Dynojet kit from Procycle.
Much more experimenting, and this is where I'm at:
FS 0.875 turns
DJ needle 4th clip from bottom
Leaner than most, but now working well with no surging and good economy, and pretty clean roll on from a closed throttle. Still no FCR, so I'll do that next. Nevertheless its the best DR650 with BST40 I've tried to date.
More of my DR650 stuff if you follow the link in my signature.