Hi, I'm having a problem with my car. lately, my car's HP decreases, and It didn't pass the emission test of LTO, I've done many things on my car, like oil change, tune-up, and even overhaul, and yet I didn't pass the emission test and I didn't regain my Car's original HP.... I'm just a student and have no Idea about car's engine so be easy on me..

my questions:
1.) how do I adjust for the air and gas ratio of my engine, my car has a computer box or CDI.
2.) How do I regain for my HP?

Car: Kia Sportage
Year: 1996
type: 2.0 dohc gasoline engine
transmision: manual


any help will be much appreciated~!