Need advice on 02 emission problem

I have an 02 Intrepid with 87K. I got a code 0440 abount a month ago. I replaced the gas cap and the check engine light stayed on. I brought it to a shop and spent $130, and they couldn't figure out what the problem was. All the hoses and connections looked good. They did a smoke test too and it was fine. They disconnected the battery and cleared the code and the light stayed off for a few weeks. I get a code now 0441, Evaporative emission control system incorrect purge flow. Not sure how I should go about fixing this. And advice out there?

i would have the shop check the ldp(leak detection pump) the switch is possibly faulty. This is famous for the vehicle

I will have my mechanic cheack the ldp. Stangely enough, the light has recently gone off. I ran it for about a week, and no light and no code. Is there just a censor on the ldp that I can change? Seeing as the light has gone off I am lead to believe it is not serious and is some type of censor problem. Any advice out there?

just a sticking switch, this is common on this vehicle.