Fault - Check Injection / High Revs

[sammy19810]

Hi Guys,
Just joined the site and hoping one of you (or more) can give me a little advice (I did run a search for the answer, but no luck)
...Being a woman, I am getting fobbed off by Renault and the typical Garage Geezers....! (I can hear you all giggling already..!)
I have a little 1.4 Megane Extreme and every single day, the engine revs like a bat out of hell and my service light comes on along with a message saying 'check injection'
If I stop, turn off the engine and re-start, it goes away for a couple of miles and then does it again. There is no pattern as to cold/warm weather, snow/rain, etc... I have also avoided motorway trips recently as I can get up to approx 55mph no bother, and then the poor little thing just struggles like hell to get up to 70mph. I have had it up to 70mph on the M27 (downhill with the wind behind me) - once...! I have had the spark plugs checked - fine. The filters cleaned and checked, all ok. Apparently my ECU is split into 2 (?) and several garages cannot access one half of it to read the fault code(s). Renault dealers (and you can hear the 'ching-ching down the phone) say its approx £80-£100 just to check the fault, then extra for parts and labour. Money isn't the issue, but I am sick and tired of hearing the builders-sigh-and-suck-through-the-teeth-sound....
Can anyone help or point me in the right direction without getting ripped off?
Thank you in advance,
Sam.

[sammy19810]

Ps, It's on an '03' plate if that's any help...?

[lee1981]

This is the exact same fault i have, has anyone got any ideas?? did you manage to sort this??