Leeds came from behind to grab a 23- 9 away to Bucharest Oaks on Saturday after Stade Franšais hammered Crociati on Thursday.
Leeds came form 6-3 down at half time to grab victory at Arcul de Triumf.
Christian Lewis-Pratt inspired Leeds to their first win of the Amlin Challenge Cup season.
The 19-year-old steered Carnegie at a rain-sodden Stadionul Arcul de Triumf with an eight-point haul before Henry Fa'afili put the game beyond doubt with an injury-time try.
The pack also played their part and were rewarded for their dominance with a second-half penalty try.
It was the third time in the past 12 months that the two sides had met having been drawn in pool stage last year.
Leeds won on both occasions, first with a narrow 10-6 victory in Romania and then a resounding 47-0 triumph at Headingley in the December double-header.
But the hosts made the brighter start to the game and opened the scoring after six minutes with a well-struck Florin Vlaicu penalty.
Vlaicu and Lewis-Pratt exchanged further penalties to bring the scores to 6-3 at the interval.
Leeds came out fired up for the second half and on 60 minutes were awarded a penalty try after a succession of scrum collapses. Lewis-Pratt converted and soon added a second penalty to give Neil Back's men a 13-6 lead.
Bucuresti never gave up and continued to chip away at Leeds' lead but a fine try finished by Samoa international Fa'afili blew the hosts away and secured the victory.
On Thursday, Stade Franšais had no trouble in thrashing Italian side Crociati on winning 57-6 in Paris.