I have a 97 grand am that looses power while driving. Sometimes its like its not getting fuel.if I let off the gas a bit it goes okay. I had the car checked out at the dealership and they said engine vacuum was low. They want to pull motor apart. I don't really want to do that unless its really really nessasary. They said there might be a blown gasket. I'm not lossing antifreeze and my oil is crystall clean. Car has 147,000 km. any suggestions?