Boost gauge is key even if you don't modify the car: It will help you determine that the turbo control system(s) are functioning properly (certainly not a given, even with a stock car).

Once you do that you'll probably realize that your next "mod" should be a proper tye wrap job and replacement of solonoids/sensors/valves that don't work.

 

Sounds like you guys are giving advice for a racing video game. hehehehe

 

I would do all of the above.

 

Guages (temp & boost), plus the downpipe can be had for less than an aftermarket radiator...not sure if this point's been brought up because I didn't read all the posts.