Volkswagen Repair: Chugging when driving, vw rabbit, long distances

Question
I have a 1980, vw rabbit, with 200000 km on it and the muffler is new, we have a new fuel filter, new coil, and the vaccum is good. Its starting up good, but as soon as we start driving and we go over a bump, uphill, downhill, long distances, it will chug like carzy and then once we slow down it will completely die out! When we let it sit for awhile it will fire up fine and go but then it will happen all over again. Whenever you step on the gas pedal the car will just lose all power and drop and we checked the vacumm and we arent sure whats going on! We took it to a mechanic and it has him stumped as well! Could we need a new fuel pump? Any information you could give me would be extremely appreciated! Thank you very much!

Answer
Kelsie,

Take out the new fuel filter and drain it into a jar.
If the gas looks rusty, your gas tank is contaminating the fuel system. You'll need to replace the tank and any components that have rust in them, such as pressure regulator, fuel distributor, injectors etc.  This could get quiet costly... perhaps you should try to find a parts car to save some money.

Good Luck,

Paul