i have a e32 and got bilstine shocks and the bavauto lowering springs and had the same problem... did you put your bump stops back in by any chance? well i didn't and like the spring fully comrpessed over every bump causeing it to make a loud clunk and feel like u ran someone over... the bump stops solved that problem now the ride is perfact well compaird to what it was... also if your old bump stops were warn pritty bad they may not be doing anything...