a top swap is a kit you can assemble or buy all together to install a supercharger from a supercharged W-body on your car. I think they full kits run around $700 but don't quote me on that. From there you will be able to install smaller pulleys to increase boost. If you find a kit without a PCM you will need one of those as well and it will need to be custom tuned. I actually am in the process of assembling a top swap from ebay and junkyard parts. Thanks to these forums I'l have the full kit for about $300 dollars and there are posts that tell you everything you need. It's not a real hard job and if you love to wrench on your own car this is a very satisfying project!
