ok. I know I am going to get flamed for this but here it is....
If you are looking to build a turbo, custom is good and it maybe cheap but the hassle isn't worth it....
If you want to do it right and save yourself the hassle then get a greddy kit and get the right fuel management system. I currrently have the new Greddy Profec EO1 with emanage in my car. The hondata is nice but it is alittle rough for running on the street the emanage and the profec are more streetable. I am currently completing my car and I am going to get it tuned over at Secret Services.
As for racing zone yes they are alittle pricey but they are worth every little penny. You don't just have to buy from them you can get it from other places too. There are alot companies and deals out their but at least if you want to keep your motor and save yourself the trouble do it right the first time.
As for the altezzas they are nice as for the exhaust loose the dual exhaust and get a full catback system and loose the cat.
Roadtoad