Reliability? Your questions are really hard to answer.

What are your plans for modding? You can never expect to have reliability or good mpg when you are going to heavily mod your car... If this is your DD I wouldn't go too crazy trying to catch up to your friends sti.... you will see alot of down time if you plan to get your car to hang with the big boys....

mpg varies how you drive and where you drive and your modifications.

If you are going to track your car several times a month then you will burn it out quick.

 

If I'm going to modify the car. I am not going farther than an exhaust and intake. I dont see that being a reliability issue. Correct me if I'm wrong. And if I do get an exhaust and intake MUST I tune it? And where do I tune it, if so. How much are tunes. I'm asking all these questions to get an idea of what i'm getting into with this vehicle.
I'm not taking it to a track. It's going to be my DD.

In terms of keeping this thing on it's top. What should be changed and when? How much maintenance am I getting into? I dont plan to punch it every second. I still want to get decent MPG. Which looks like 22 if babied. And would an exhaust and intake up the MPG?