No such nice neat fixes on that guy. Mechanical fuel pump and nothing electronic anywhere but the ignition module.
Probably a Carb/choke problem. It also could probably benefit from some additional timing.
I would strongly suggest that you give the shop another try at it. That carb gave us fits when the cars were in warrantee and it didn't get any easier when the customers started paying for it.
Since you already have given them some money the path to repair should be cheaper here. I would be prepared to leave it with them for a couple days so that they have plenty of oportunities to verify their fix. They might need to see the warm up cycle two or three times to be sure.
As it turns out I will be in San Antonio tomorrow for a Diagnostic Workshop being held at Rhine West (a BMW specialist). I will be at the La Quinta 333 NE Loop 410 tomorrow evening and would be glad to drive it for you and verify that warm operation is up to snuff. I don't know the room # yet but if you call for me I should be there. Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician