I just purchased my wife a 2007 S40 with 12,500 miles.  The woman we purchased it from was the second owner.
The first day it ran like a champ.  I filled it up with 91 oct with ethenol.  I didn't realize it contained ethenol until I had filled it.  I used 91 because the lady said that is all she ever put in it (her baby as she refered to the bike).  Anyway bike ran great the rest of the night.
I deciede to ride the bike to work the next morning, only 5 miles away.  When I started the bike that mornig I engaged the choke for less than a minute, as it didn't seem to make much if any diference.  A mile from work the bike started giving me trouble.  It would die as soon as I let off the throttle.  I could get it started by applying throttle.  The problem persisted on the way home cutting out unless I had the rpms up.  Any suggestions?  THX

How long did it sit? Was it in a storage shed, where it got a zillion degrees? Your vac line may have crapped out. Look at your tires, are they dry rotted? Rubber is rubber, ya know.. You may have gotten lucky,, it ran okay because the dried gunk in the bowl hadnt softened enough to start moving, you may need to drain the bowl a few times or just pull it & clean it & have a look at the jets,
Ive found a puddle of green crap in the carb bowls Ive let sit long enough to evaporate the gas off. Its a simple hassle, you know it runs, thers crud in the fuel of the vac line is toast or both,.
Regular gas is the answer on these.

Sounds like a real good plan of attack,

My thoughts usually get me in trouble in one way or another.

Goes to show, always revert back to the last thing you did as simple as it may be