Stalling and overall wierd behavior from your 240 more then likely means that your fuel relay has starting to go bad. It's $25-50 depending on where you buy it.

I've owned Volvo's for years...whenever you have a fuel related problem (i.e., fails to start in hot weather, starts but stalls on accel, drives fine for a while then stalls but restarts okay, etc.,) you should replace the plastic fuel relay ($25-50 depending on where you buy it). I've had an 85 240 ...

I purchased a replacement radio for my daughter's 850. I actually took the radio into the Volvo dealer and he looked up the code for me. Works like a champ

I used to own a 1985 Volvo 240 Wagon that did exactly the same thing. The dealer swore up and down that they could not replicate the problem. I took it to a second mechanic who replaced the fuel relay (little white plastic box). The problem was fixed immediately.

I also have a 1991 Volvo 240 sedan ...

Yes your car did come with one. I bought an 1985 Volvo 240 wagon while stationed in Europe. They removed the converter while I was overseas but reinstalled it once the car was shipped to the States.