Welcome cstew69!
I think it isn't exactly the same engine - ALMS TT has a bigger tubo(?)K04, different injectors, improved DV, and software.
That being said, you can do a chip and also upgrade your diverter valve (probably inlet hose as well) and get good performance gains.
Look at GIAC and APR as first tier vendors - reputable and a good dealer network. Some people run Wetterauer, Neuspeed, and RevoTech.
Then there is an exhaust to possibly do - and suspension, etc.

 

the tt225 is substantially different. 225 is trans vs. passat is long, upgraded engine internals, and other items mentioned above.

chip alone should bring you to around 200hp or so. for the 99, you can get the neuspeed chip, which is only $180. that's by far the best hp for the buck. others start costing quite a bit more. k04 upgrade brings you to about 230-250. pes t-28 or apr stage 3 brings you to 280-290. more power is possible with custom work, but cost adds up quickly.

fmic, exhaust, and intake recommended for the k04 and up.

 

Stewart and D.Passat- thanks for the info. This is my first turbo car, so bare with me.... What is the diverter valve? Is that the valve that routes exhaust gases either TO or AROUND the turbo? By "inlet hose", is that the turbo inlet hose? If I get, say, a Neuspeed chip, do I have to get any other hardware to go with it, to compensate for the increased hp? What's fmic? Can you guys recommend any specific exhaust manufacturers?
Thx again. C.

 

A diverter valve releases excess presure from the system.
On most 1.8Ts a chip means you should get an upgraded DV to handle excess boost. However, a neuspeed chip doesn't seem to be the best choice unless CARB approval is important.
FMIC= Front Mounted Intercooler

 

looks like neuspeed doubled their price to 350, so scratch that. just get apr or giac.