What's the difference between an Audi TT and a TTS?

From what I've read, the TT has 200hp while the TTS has 272hp. Do they have the same engine with the same turbo with the difference in power coming from more aggressive ECU tuning? Can a standard TT have its ECU flashed to produce the same power/torque as a TTS and what is the company that does the tuning? Besides the TTS badging and silver colored mirrors, does a TTS have any other significant difference such as better/firmer suspension? Are they both quattro or is the TT just a FWD car? Thanks.