it sounds like ricer badges to me. There are not many aftermarket turbo kits out there and for someone to put one on and remove it with only 2k miles would be surprising. Those kits take a lot of work to install. If they come with badges at all, I seriously doubt it would say "Turbo Edition", rather than "Turbo" or the kit manufacturer's name.
If you are worried about the car having had an aftermarket kit, inspect the exhaust, radiator, and air intake for evidence that parts were removed and put back on. The other thing you can do is ask them to read the computer. GM claims the checkdigits or something changes when you program the computer, even if you put all the settings back to stock. Any turbo kit would require a major reprogram. The computer test is a serious consideration since GM would use that to deny powertrain warranty issues.
Lastly you could have them R&R the oil and a do a compression test if anything else looks suspicous.
