As my MB 300E 1989 was functioning badly, my mechanic discovered that a species of plastic membrane with 6 circles in auto relief, that is in the interior of fuel distributor is with a small perforation in one of those circles, corresponding to one of the injectors.

We don't find this small component to substitute and I don't imagine one of the most expensive parts of the automobile is made unusable because of a component, that me seems to be of very low cost.

The related membrane is sufficiently fragile and must be common its replacement.

Can you help me?

I do not know if you are aware but, the mentality here in the USA is to replace the whole defective part instead of fixing the part. Here, labor is usually the most expensive part in a repair. This is specially true in MB's. I recently replaced my fuel distributor with a used one, which I bought in e-bay (it works great). Rebuilt fuel distributors are over $400.
I know labor in south america is VERY cheap compared to the USA. My suggestion would be to try to find a BOSCH authorized repair facility and see if they can provide the part or maybe Steve Brotherton can help you out...
Good luck!

__________________
J.H.
'86 300E