Thank you all for your replies,

After much thinking about this problem, I decided to disassemble and reinstall again the throttle body, fuel distributor and all the lines, and checking vacumm lines for any leaks while "tightening" them just using my fingers, and reinstalled every single screw very carefully and cleaned the wires and idle valve.

After that, I noticed that two injectors were loose, so I went to my parts car and took the other ones, which appeared to be in better condition, and installed them back very carefully. I was very fortunate that I found a K&N filter in that parts car and went to buy a "recharger" to clean it.

I took a very quick test drive for about five miles and the car is much better, it accelerates very easily and reached 75mph and then 80 without need of pressing the gas pedal too hard, just moderately. The car is not perfect but far better than months before. Cool, problem fixed !!!!!!!!!!!!!

Anyways, since I have an extra car for parts, I think I will change the exhaust pipes including the cats in the near future, mine is too noisy already and I don't think it will be a big problem.