2000 si really rough shakey idle
 

I'm only the seconded owner of this 00 si I bought it with 71000 on it now its has 185000 so about 6 months ago I'm going down the highway and i felt something give loose it felt like in the peddle like a lose of power and when i came to the first light it started this rough idle shit. So I've replaced everything from the plugs back and still the same thing. So I'm thinking its burnt valves because of the misfires on 2 and 3. I really just need to know if its a sensor or am I gonna have to break the head down and rebuild it up. HELP PLEASE THANKS