Engine Upgrades for UrS4/S6

[Trevor and Cara Frank <tcfrank@home.net>]

I have been looking at the different tuners and what they have to offer,
this brought me to the question.  What are the logical steps for
upgrading the motor and keeping the costs down?  In particular I have
been looking at TAP because there claims show more horsepower for less
money.  But are there dangers in running a Stage 2-4 set up +80-110 hp
without going to the RS2 manifold or Turbo or a better intercooler.  It
also seems that the underhood temperature and the temp of the turbo may
become a factor.  I was wondering if anyone has used a water injection
system to try to control the problems associated with such mods, i.e.
knock, high engine temp, high intake air temp.  Has anyone tryed to
build ther own exhaust manifold, 321 S.S. any pitfalls, more work then
it is worth. 

Any thoughts?