Advise on building a HO engine

[Zsolt]

I have been thinking about building a second high performance engine for
my car (88 5ktq) from the ground up and when it's finished, just drop it
in the car. I would like to keep it a 10 valve as I am sure I can find
one easily, and the 200 quattro with 20 valve engines have never been
imported to Canada. (I have never seen one anyway)

This would include EFI, a bigger more efficient turbo, 3" free flow
exhaust and a bigger intercooler, but I am not sure as I never
researched this what other things I should consider. What internal
upgrades can I do to this engine to get the most out of it, while it's
still street driveable (cam, pistons, bigger valves, intake/exhaust
manifold etc.)? How about other external modifications?

Please let me know what you all think.
Thanks for your input,
   Zsolt