For the downpipe, I chose the CG Precision DS-1 because it seemed the best for no CEL. A lot of others will trigger a CEL. I didn't want to mess with O2 sensors. The other one you could look at is the Active Autowerke downpipe - they also guarantee no CEL.
https://x-ph.com/cg-precision-ds-1-h...npipe-bmw-b58/
https://x-ph.com/active-autowerke-aa...-b58-downpipe/
I got my eibach springs here :
https://www.tunershop.com/shop/eibac...5-pro-kit.html
So far they ride great. Comfort very similar to OEM and a nice 2cm drop.