Romania had about 400 Mig-21 bought during the cold war when it was an ally of USSR. In the begining of 2000s, they modernized about 70 Mig to NATO standards [1]. There were frequent issues with them with about 20 fallen in 30 years. The aircraft were modernized but it only included the avionics and elecronic+weapons to NATO standard, I think the engines remained original. After Romania left the Warsaw pact, the Russian didn't provide engines or parts anymore.

[1] https://www.hotnews.ro/stiri-defense-25405860-cate-avioane-v...