My vr6 galant 1994 model doesn't perform well, coz' when i started it, it sounds like a volkswagon beetle! the 3rd & 6th spark plug does'nt work... help me!

1342 thats right!!

There are 3 simple ways to troubleshoot this: Gas, Spark, or Air. The car is not getting enough of one of these. If it turns over you have battery power.

Gas - Is there enough?
Spark - Remove each plug and lay it close to the motor and have someone turn it over while you verify the spark for each cylinder.
Air - Verify the air filter is not clogged

Sounds like wet or moist spark plug wires. If this also occurs during early morning high dew point humid air, then you may have spark plug wires shorting out.

Replace wires.

try spraying wet start on the cap leads and coil.

check your airflow meter and camshaft sensor but i belive its your camshaft sensor

Replace the coils?

Very common for the coil pack to fail on this model, also the plugs are a pain to change and are often left, try these first.

IF THE BATTERY HAS A FULL CHARGE ,THEN IT SOUNDS LIKE YOU HAVE A BAD STARTER,BUT I WOULD CHECK ALL OF THE FUSES, & RELAYS, BECAUSE IT COULD HAVE A BLOWN IGN,OR START FUSE, OR A BAD STARTER RELAY.

Maybe a stupid suggestion, but check the oil amount in the gearbox. It must be done with the motor running. I did´nt know that and checked it motor off when the level on the dipstick was fine. When I checked it motor running it was too low. I filled it up and the gearbox works fine...

may be it is the engine that good condition...