Looking for brainiac's advice, I'm new to Audi's!

I just got a 2003 Audi A4 1.8T Quattro, 54,000 miles, and its in great shape. I'm looking to (slowly!) mod it, and I am probing the immense wealth of info contained herein to get suggestions. As far as I know, the car is stock, but I can hit the gear limit in 5th (138MPH~ish on the speedo, but the GPS says I'm doing 133MPH~ish) and I have heard that there is supposed to be a 130MPH speed limiter. I am fairly certain that this car hasn't been chipped (make that 100%), but again, I just got it last week. I haven't poked around with it much, mostly just driving. She's a hell of a lot faster than that 97 Subaru Legacy Outback I had, then again, that thing was close to dead.

I would like to get a chip for it, but I want to make sure I dont lose my peak torque at 1900RPM. I know chipping it boost's the power, but what does it do to the power curves? I am thinking about the APR chip with the injectors they sell on their site.

I am also looking to get an exhaust, (I'm in Vermont, so no test pipe, she has to pass California style emissions) and I would like to ditch the center muffler. Does anyone know about high-flow Cats and their effects on emissions?

Some other mods will be an intake (K&N, Carbonio? advice?) better DV (I would LOVE to have the PSSH sound, but after reading about the diverter valves here, I don't thow if that would be wise), and maybe later on some Brembo brakes.

I'm a big fan of inexpensive (read: not "cheapo ricer crap") mods, so any suggestions are welcome. Do please keep in mind that this is my daily driver, I live in Vermont, and as much as I would love to not have to, I have to drive in wet, cold, slush, through pot holes, over frost heaves, and on dirt roads.

Another thought, I would like to get a spoiler, not a NASA wing (stupid Hondas...), but a small spoiler. The back end of my A4 is the only complaint about the car, and even though its not that bad, I feel it could be better. Not a high priority really, but if anyone knows of good spoilers, suggestions are certainly welcome.

And with that, its off to browse the forums some more. Thanks in advance!