My son And I bought a 1990 honda civic hatch back for him as a first car... question he lost power wile driving so I replaced the spark plugs and I noticed oil burnt plug at #2 cylinder and the car does puff blue a little when starting could this be a dropped valve or stuck valve, valve guides, sludge in the engine, because we did put in fuel injector cleaner in and some methalhydrate ?(spelling ) into the fuel tank because it had sat for a wile before we bought it... so am I looking at pulling the top end off or what please someone throw me a bone...

Likely, the valve seals need replacing. Start using 5W-30 full-synthetic engine oil; e.g. Mobil 1. This will safely clean the engine up and provide maximum protection.