The brunt of your cost is in the labor obviously. They're taking off the top of your intake manifold and dipping it in a chemical solution. This will clean out all the carbon buildup inside. With everything off, they'll probably(IE:they should) clean your throttle body, IACV, and EGR passage. Who knows. My mechanic just did this last week for a car. It was 97 GLe w/106k. That thing was filthy. But the machine shop is right around the corner. So he took it there. I think it cost them 200-250. Somwhere in that neighbor hood. I dont think your really getting ripped off. Your just paying for Dealership labor. I think the 5 hrs is pretty accurate for taking off the manifold and putting it back.