1. Jayco is a rip off stay away..he is actualy banned from most zx2 sites.
2. Cat can cause bad readings that MAY cause tranny issues...but get the tranny looked at anyway.
3. Iceman or Roush or Roush style are teh 3 best to get for intakes, Iceman, and Roush Style from ZXtuner.com are teh cheapest.the Roush is typicly 300 is you can find one(very rare)
4. if you have the stock 15in rims, 205/22 is the biggest tire you can go.
5. the faster you accelerate the harder the tranny will shift..but that doesnt mean its still not an issue.