If you are not ready to give the dealer another $120.00 for diagnosis then you'd better get that way fast. The odds of it being the same part 5 months later are not that good and even if it is chances are good that it will get buried and they will find something else that is wrong and charge you for it. When you took it in the first time and the light came back on a week later that was complete and total bullshit and the service manager knew it, that is why he waived the additional diagnostic charge. Now 5 months later you probably do have another problem that is not related to what they found in your first two trips through. The evap systems in the later cars, hell in all of the cars, leaves a lot to be desired both in terms of diagnostic capabilities and cost on the parts. There are some decent code readers out there, you can get some nice stuff from OTC at the tool warehouse and then there are PC based systems as well that are pretty nifty too. If you have intentions of owning any later model Volvos I would get a tool that can do CAN systems, take a look at the OTC stuff. You can get into some of their scan tools for around $300.00 and they will do CAN protocols as well as a bunch of other stuff too.

Mark