I'm looking for anything and everything to enhance the performance of my 1998 4.6L Expedition. I already have an exhaust, air intake, chip, and headers. I'm looking for big power adders other than superchargers or nitrous. I thought about getting a new camshaft with valve springs, maybe a new intake manifold, maybe even new cylinder heads. Also, I was wondering how much it might cost to have my engine bored out, or to be port and polished. Does anyone know about how much it would cost to get some of those things installed. One place quoted me almost 2k just to buy the camshaft and valve springs, and get them installed.