Actually, I don't know what he is talking about. The evaporative emission systems have a vapor separator designed into the tank on most cars. They used to be separate.
I read a lot of posts asking questions, where previous parts were installed. It seems that there must be a lot of trial and error testing going on. It would be my position that any part being installed would solve some specific test deficiency. This is proper testing. If you think a fuel pump is failing at idle (the most unlikeliest senario I can think of) it would more likely be electrical (relay etc).
The hypothesis should be backed by fuel pressure test readings which then are verified upon replacement. Believe me, whatever is occuring has a result that can be measured by more than the seat of your pants (the seat of your pants said the car died).
I personally would go for an OVP relay if I was shot-gunning parts. The test that would prove it would start with measuring the current through the idle control motor. Low idle that stalls the car will get readings below 500ma with 600+ being appropriate. The OVP relay causes the low idle by providing a weak circuit that reduces the current even with the controller trying its hardest.
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician