> - Importing western materials and parts was not expressly forbidden (though certainly not politically popular). But Poland (like a lot of Soviet countries) was undergoing a currency crunch. Possession of foreign currency was illegal and importing materials did not do favorable things for their "fake" exchange rates. The operation was probably contingent on generating more foreign dollars than they spent.
Poland was embargoed so it was tricky to obtain western components. Poles had to pay for them in hard currency, because Polish Zloty was not a convertible currency. There were two exchange rates, the official one at which hard currency was exchanged into zlotys and the the unofficial street rate used by illegal money changers. Those rates varied wildly. Poles who did earn hard currency would have currency accounts, but were forbidden from withdrawing actual dollars or german marks, instead they were given special tokens they could spend in the so-called internal export shops selling western food, clothes, household equipment, radios, TVs, and even toilet paper, because that was one of the things communism struggled with near its end. Those fake dollars had a lower exchange rate on the street.
Ownership of real foreign currency was forbidden as was possession of a passport. There were two types of passports, one for the countries of the Soviet block and the other for the whole world. You had to bring your passport to the local police station for safe keeping and interrogation. Passports would not be issued to all members of a household to prevent them from fleeing the country.
Economically, Poland was getting massively squeezed by the Soviet Union who ordered a lot of ships to be built in the Polish shipyards, but would only pay for them in "transferrable rubles", the currency which was not convertible and pretty much useless. https://www.researchgate.net/publication/305054272_The_Trans... The exchange rate vs. local currencies was controlled by Moscow. In order to deliver those ships to Russia, Poles had to purchase materials and equipment outside of the Eastern Block and pay for it in hard currency. Eastern European countries quickly developed a barter system, but non-Eastern European suppliers wanted to be paid in US dollars. Poland tried to sell its agricultural and industrial output, but could not compete with Western suppliers so the earning were meagre. This has led to lowering of living standards beyond which people had enough of communists and the party was over.