Feinberg-Mngomezulu captains Stormers into Champions Cup last 16
Feinberg-Mngomezulu, 23, slotted two conversions and a penalty as his side crossed five times in total in rainy conditions in Cape Town as they bounced back from last Sunday's 61-10 thumping at Harlequins.
Defeat left the Tigers' last 16 chances hanging by a thread, with La Rochelle needing only a single point form their home match with Quins to snatch the last knock-out spot from Pool 3.
Four-time winners Leinster produced a solid comeback to beat Bayonne 22-13 having already made sure of their knock-out berth from the group.