I have a 1995 volvo 855 turbo. lately, it is so weak to start engine after fill up tank. it starts fine other time. it only happens right after fill up tank. sometime, it even stalls. i took it to volvo dealer and they said it should not be a problem if i do not fill up all the way, and it works fine, but it starts a little bit weak. i feel like gas milage is not good lately.
can anyone suggest me what should i do or what is going on?
thank you.

I've had the same problem with my car for 2 years, until recently the garage replaced a electronic valve of some sort of air filter devise(sorry for not knowing what the correct name was). The valve was suppose to make the air ran through one way only, since it was broken, air leaks through it and also caused the boost did not hold.
I am not 100% sure if it's your problem, but as for my car, starts at once every time out of gas station.
Hope someone from the board can help you with the exact name of the part.