I not sure if you are still having issues. As for the hard to start angle I think I have an idea. I know all of the modern BMWs have a saddle type fuel tank to accommodate the driveshaft. This means that there is one fuel pump and also a siphon pump to transfer fuel from the side without a pump to the side with the pump. I was thinking maybe if you parked on a specific angle where the fuel pooled to the side with the siphon pump it has no way to deliver it to the pump side. I'm not familiar with e30s however and don't know if the saddle type gas tank goes back that far.
