I took my wife's 2001 Mazda Tribute in for service because when cold starting the engine idles rough and stalls. Once it's run for a couple of minutes it's okay. They said it needed upper and lower air intake gaskets due to a (vacuum?) leak. Including the $90 diagnostic fee, 80 +30 for gasket kits, the total will be $515 +tax. I haven't had them do the work yet since they had to order the gasket kit. A day after they looked at it the check engine light came on, I used my scanner and it came up with a 1131 and 1151 error- Heated O2 sensor - lean (I think they both said left bank, #1 , I don't have the error code book here at work). Does the gaskets replacement they are suggesting sound like it could be the actual cause and resolution? I don't want to think they are charging me over $500 and will just replace a sensor or two or replace the gaskets if they are needed. Thanks in advanced for any help with this. I'm lost when it comes to anything on cars made after the early 70's, too many hoses and sensors.