I'll take it you're in the US so being a brit I can only go on what I read in these posts (feel free anyone to correct me if I'm wrong) - There is a company called DINAN over there which I hear tune Beamers to the hilt and most people reflect of them very well. Also there is good old AC Schnitzer who do everything from wheels to body kits to engine tuning chips - although I don't know if either have moved on to the E60 yet. From what I can gather though, both are VERY expensive. The alternative is to possibly do a mix of the two or buy each part you require individually (intake, chip etc.) from various shops and online stores - doing a google on "BMW TUNING PARTS" should bring up plenty of sites that sell performance parts for both 530 and 545.