OK it's an import but was it bought from a proper Ford dealer with warranty?

You may be able to get Ford to change the ECU for one that's mapped to your 91RON petrol. Or at least the Euro III set up instead of the Euro IV that yours is trying to run to, it will run better with the Octane booster then.

If not then you may have to get the car re-mapped yourself.

Surely people like DreamScience and Bluefin would be able to cater for this??

Also, I'm not tying to teach you to suck eggs but there must be a petrol station somewhere that sells the higher octane fuel.
Why don't you do some research on the web to see what other stations are offereing?

Even if you have to go a bit out of your way??

Mmm I've just done a bit of research and it looks like you can only get "Magna" which is 88RON and "Prenium" which is still only 92 RON

I think you need to look at buying something like a Bluefin and getting them to do a Map for the 92RON fuel. If it's a genuine Ford import though you should make them sort it for you as Europe spec Fiesta STs are mapped to run on 95 RON Unleaded ONLY. The standard model Fiestas have a bit of adaptability in their programmes and can sense when the fuel is a bit crap and back everything off to try and adapt but ST will not, it will only run on 95RON.

The comment the dealer made about it being the valves suggest you may also need to use an addative that contains an upper cylinder lubricant. BUT MAKE SURE IT IS NOT A LEAD SUBSTITUTE. I'm sure people like Slick 50 do an Upper Cylinder treatment, try at your motor store or see if you can order stuff online?
Also you need to make sure you change the fuel filter very regularily from what I have been reading.

Good luck mate, I hope you get it sorted

Hmm.. its way more complicated than i thought! Im taking my car to the dealer next week, and im telling them exatly that "appareantly there is a problem with the mapping of the ECU, its set to 95RON and it needs to be in 91RON", plus i will check out the store for some additives, went in today but was closed till monday lol, well hope this works, BTW if the dealer does the mapping how long would it take? Thanks everybody

It would be an exchange ECU so they would have to order it and have it shipped over.

Then about 2 hours fitted. Tell them they need to contact the European technical support to find out what can be done to run the car on your Fuel.

A bit of advice, Why not join the South African Fiesta ST Forum, those guys on there are really helpful and I know they have some crappy Fuel as well but their cars are not Euro imports they are built especially for SA.

Site: http://www.fordstownerssa.co.za/

ST Forums: http://www.fordstownerssa.co.za/forums/

You may want to tell the dealer that this may also be a Throttle body fault if the car is allready mapped to run on 91.

It looks like the SA guys are suffering with their Throttle bodies.