1. An AWD upgrade is a bolt in proposition from all accounts. you just need to make sure you have the right model.
2. Your better of Buying a WRX half cut and sticking that in.
3. see #2
4. You can get GT/GTB bonnet scoop for these cars, and the Half cut should come with a TMIC, although you are better of  IMO, going for a FMIC setup.

Hope this helps.

Hi mate,

Welcome to the site..

Check out amauto.com.au for an idea..

A half cut or front cut is a crashed/rolled car that has been chopped to sell for parts, usually engine, exhaust + computer etc plus front brakes typically get re-used as upgrades for GL/GX and even RX and B4 conversions..  Instead of buying these parts separately you truck in the cut-off front of an entire car and strip it for the good bits..  make sense?  A few people on this site have done this themselves, but for most of us, it's a good idea to pay someone who has experience to get it right first time..  The site I gave you above is a good example of those who do it well..

The WRX engine is an affordable way to put a turbo in your car, much more common than bolting a turbo onto your ej22..

FMIC & TMIC are front intercooler and top intercooler..  IMO is 'in my opinion'..  there's a bunch more..  just use google to find out what they are when someone uses them..