Cabby go down at 100 km/h

Hi all guys, this is my first post there so sorry, sorry for my bad english!

I have a problem with my cabby, it's a '82 1100cc. I tried to fix it in different method but i can't find the problem!

The problem is:
I start the car (it start without problem) and i can drive it without no problem on city road.
When i take highway i accelerate and when i reach about 100 km/h the car begin to lose power and it doesn't go more, so i have to stop at the side of the road. If i wait 2 minutes stopped, turned off and turned on the car i can go yet but if i reach again that speed it will do the same thing and again the same story. The speed it's indicative, it happen at 100/110 km/h on my speedmeter!
I try to change fuel pomp, petrol tubes, clean carburator, contacts, condenser, new candels… i don't know what it can be!

Someone can help me?
I don't know what i can do now…
Thanks all!

Welcome to the Club first of all Andrea.

Now I've not heard of that problem before but I'm giving your post a 'Bump' because I'm sure there's a member or two out there that just might have a good idea what the problem is and how to fix it!  

Have you removed the petrol pick up pipe from inside the petrol tank and checked that?

Hi man, thanks for the replys.
It will be the next work and check i have to do.
A friend of mine say the same thing, probably something wrong in the tank and when i go more fast petrol doesn't arrive good