CO high in ITV gasoline without catalyst

Hello, I have a renault 21 of 1987, Txe Gasolina 2.0 version does not carry catalyst and is multipunto injection.

My problem is that the ITV gave 9% CO and there is no way to lower it.
At the moment I have done this:

- Change of filters, spark plugs.
- Mix potentiometer change.
- Fuel pressure regulator check.
- Check as an admission collector sprinkling oil and does not suck or stop even slowed down.
- I always slows constant at 900.
- Treatment of gasoline and pre ITV injectors.
- Enter the ITV carrying the car completely revolutionized.

What mechanics have told me:
- They don't catch it because it can be anything and is very difficult and expensive.
- That is because the hoops are worn and there escapes the fuel (rich mixture).
- That is because the escape is new and does not retain gases (?).

What I have left to look:
- Cleaning of injectors.

I do not want to sell the car apart that I can neither with the unfavorable ITV because you can not change name, I have to wait for it to leave or sell it without papers but I do not want trouble, I would prefer to keep it because the car is going very well and I love it.
Any advice?

You would have to measure the pressure of gasoline on a ramp (if you have not already done it) and if you can, check that the injectors do not drip off (it is not enough Make it inject as if it were not yet hot (more) and the thermostat of its working temperature. Finally, that it is at its correct ignition point and distribution well; These cars when they are old one has to look at them almost everything, if it is a thing of injectors you can search in scrapping. You can try to attach a catalyst (even if you do not take it) they reduce a lot. Well, there is luck pptrola !!