You might be able to get away with just running a bottle of fuel injector cleaner through the fuel tank. (mechanics.stackexchange.com)
Rough idle can be caused by dirty fuel injectors, incorrect idle speed, exhaust restrictions, vacuum leaks, incorrectly installed or damaged spark plugs, a defective or clogged fuel pump or fuel filter, failing electrical components such as the ignition control module,... (yourmechanic.com)
Having said that even our petrol wrecks havoc with todays modern injectors because it is down to the Euro 2 fuel... its just too high in sulfur content which why you see a higher failure rate for fuel injectors for modern cars especially performance cars.... (paultan.org)