This car was for sale in May, 2007, through Ferrari of Central Florida: Argento Nürburgring with Cuoio interior, shields, aluminum calipers, Challenge grille, Capristo exhaust, 10,386 miles. It had a belt service in January, 2005, and a 10K mile service in May, 2005; at the time, they were asking $134,500.
Mercedes-Benz of South Orlando had it for sale in June, 2007.
Then it was back at Central in February, 2008, with 10,663 miles, for $115,000; still liveried in the aforementioned specifications.
A month later it was for sale through Elite Auto Buy, Inc., of Georgia, 10,668 miles, $108,500 - still stock.
In November, 2011, it was for sale on eBay at Auto Junction of Phoenix, AZ, with 15,136 miles. Still listed as Argento Nürburgring with Cuoio interior - no mention of the aftermarket modifications.
If it was still stock in November, and the current owner has spent, let's say, the last 12+ weeks putting fifty grand into a car for which he's only asking $85K - why is he selling it in the first place? The only way that wouldn't seem odd to me is if he owns an aftermarket tuning company and just buys cars, mods them and then sells them (cheaply?) in the hopes that word of mouth will buy him notoriety in the tuner world.
The serial number you posted is definitely correct, right? 122455? Where is the car currently located? Are you in the same city as the car?
The other replies in this thread are really valuable information and advice that should be considered before making a final decision. And while a PPI won't tell you market value of a car as extensively modified as this one, having the technician inspect installation quality of all engine-related and electrical components is serious peace of mind. Good luck, and please keep us posted as you continue with your search and/or acquisition process.
I need an Aventador!