I am looking at purchasing a 1999 Carrera, and I've read the Buyer's Guide (good stuff there, thanks!) as well as browsing through this and other forums. This 1999 has a completely rebuilt 3.4L, including new sleaves, and all the work has been done by a guy who appears to know his stuff. Can anyone give me a rough idea of what value ($) this adds to the purchase price? I'm more than willing to go over KBB for this car, given the new engine as well as some other modifications/fixes, but I am at a loss trying to put a dollar value to the work.