I think that's a scammer ad. They ask you to send a money order right away and the car doesn't even exist.
The ad has been removed, so I think I'm on to something.
If you're looking at used WRX's or STI's, the easiest way to tell if the car has been modified or not is to look for the stock heat shield(little metal piece with the cartoon hand on it). They have to be cut in order to fit an aftermarket downpipe on. They also attach using like 8 screws, so they're hard to put back on once removed.
If it's removed or cut, you know the car has been modified. Modified cars aren't bad if the owner can tell you the history. If it's modified and sitting at a used car lot, move along.
2005 WRX Cobb Stage 2