Problem with my golf - Please help

I drive a standard 85 golf GTI 8v, I live in Lebanon and cars are wicked expensive, I bought it for like 2 gran with 136k on it, it was all messed up, so we put $2500 into it, we changed the injectors, changed oil pump, fuel pump, cleaned the carburetor, replaced the wiring harness, it ran quite nicely until a few days ago.

What it does is it kicks sometimes, like pretend you're driving on second gear on about 5k rpm, drop ur foot and kick the pedal within half a second, thats what it would do. Then sometimes the rpm drops for a few seconds, no engine response, then I have to play with the gear like crazy and clutch and pedal, then the rpm will go back up followed by a very loud backfire (not sure if fire comes out or something). Then usually after all that, the car will just stop responding and turn off. The car will not turn on after that (sometimes it will), keeping in mind the engine IS turning over. The first mechanic came and fixed a loose wire and it worked like a dream for the rest of the day. The day after that the same thing happened in the middle of nowhere, then out of luck the first car that passed by was a mechanic, he changed something by the spark plugs, like a piece of metal the size of my pinkie nail, took some cash from me for the work then left and it worked. However the problem still persists.

http://media.photobucket.com/image/golf%20GTI%20MK2%20engine/tapie/DSC00407.jpg

I don't know what the thing he changed is called, but its a circle looking thing thats like brown/orange by the radiator piping, an inch above the shiny metal thing on top of the grille.

Thats pretty much it, my guesses are its something electrical, something thats preventing the spark plugs combusting the fuel in the cylinders.

Does anybody know what the problem could be?

Thanks everyone who replied, I put $2500 into fixing the car and its still not running well, thanks again guys.

Common problem with those cars is coil going south. When the car dies, check for spark coming off the coil. If no spark, check for signal going into the coil. If you have signal from the pcm and no spark, replace the coil.

The wiring harness connector is another common problem with those cars.