87 325 runs good when cold then starts dieing idling up and down

I would suggest changing the FUEL PRESSURE REGULATOR mounted on the fuel rail with a vac line going to it.
it could be a number of things, if it dies when its warmed up it is most likely a faulty fuel pump on its way out, but it could be anything, need more info. 
Check the spark plugs, change the fuel filter, when was the last time the timing belt was done? how many miles are on it? 
lastly sometimes these cars have old relays, as found on the e28, they were known for not working when they warmed up, change the fuel pump relay with a new one ($7) just to be safe.