Allah k bande, if there was any such limit, how in the world will your car go beyond or till 180km in D3.
there are no security/speed limits in your car. simplest thing is to get your car tuned. if that doesnt solve the problem, then you need to get your injectors checked, fuel pump checked and so on. check your ail filter, plugs etc etc.
just remember, your civic has no issues as u think it has.
i had a japanese civic (ferio) a year ago. the car wouldnt cross 195km no matter what u did. even though a lot of pedal was remaining. i got each and everything checked. even went on mway for a test drive with the scanner installed to check all values when driving, everything turned out to be perfect. the mechanic then suggested to get some modifications done to which i declined.
wait for some other expert opinions before finally deciding what to do.