Volvo Repair: V70 endless problems (OBD p410 now), camshaft sensor, head gasket

Question
Hi, thanks for considering my question.  I have a '98 V70 that has become my worst nightmare. I bought it 2 years ago with 68K miles. It now has 88K miles. Ever since I bought it  we had been using a lot of oil.  We it was determined that the head gasket needed replacment -- which we did. Then a week and a half after getting the car back the the new head gasket, the car began leaking oil like mad. It was discovered that the camshaft sensor seal had failed and we had to replace that. I then got it back from getting the seal replaced, the next day the "check engine" light came on again. this time my mechanic says the OBD showed a p410 code. My question for you are:

a. what are my potential problems that p410 is announcing?

b. could all of the work that was done with the replacement of the head gasket or the replacement of the camshaft seal have caused the p410 error?

Thanks,

Andy Taylor
Seattle

Answer
were did you fix you car volvo delaer ?i dont thing you had problem with headgasket but anyway .with the foult code you have problem in air pump system moste the time it will be air pump check valve and realy  replaced   .take it to volvo dealer get diagnosed and than let your mechanic  fix what they say is bad god luck