It depends on what you are looking for. All 996 TT ECU have to have chip melted away from ECU unit then programed and then reapplied. Porsche NA now puts plastic over the welds to show that they have been tampered with or not. Luckily no one checks within the unit itself. The ultimate in quality is ruf (Weissach). They are churning out extremely dependable 585HP now, but they are also the most expensive. If you want stage III or higher I would suggest ImagineAuto first then EVO next. Both are very good with their tuning and great with customer service. Your prices range from 3200 for Stage 1 to 29K for stage IV and up. The power is hard to describe with words. If you want a very inexpensive and now proven Stage 1 that is putting the 996TT's in the 55O HP range I would suggest Upsolute at $500. Like me and the others on 6speedonline.com we are all putting on performance mufflers, 24K Turbos, ECU upgrade (what I described above), Bailey, or Billet diverter valves, K&N type filters, and short shifters. Then when you have that extreme power the people are then changing suspensions, and most important of them all in mods is the brakes...

Hope this helps.