A week after plundering 13 tries in an 85-5 win in Spain over Bizkaia Gernika in Pool Two, the Warriors made it an unlucky afternoon for the Italians as they added 14 more at Sixways.
Lemi weighed in with two tries in each half to equal All Black wing Rico Gear's club European record against GRAN Parma four seasons ago, but his 20 points were beaten by outside half Joe Carlisle.
Seven days on from notching 20 points in Spain, Carlisle eclipsed Shane Drahm's club European record of 21 points in a match against Montauban four years ago as he ended with a match haul of 30 from 10 conversions and two tries.
Also in Pool Two, Gernika were hammered 90-12 by Perpignan. They ran in 14 tries, with winger Adrien Plane responsible for five alone.
London Irish made it a perfect 10 points out of 10 in their opening two games in Pool One with a 69-26 home win over Mont-de-Marsan. There were 11 tries to add to their six in France the previous weekend as they made it back-to-back wins over Top 14 clubs.
Having picked up 11 points in the 43-16 win at Bordeaux-Begles in Round 1, outside half Ian Humphreys helped himself to 13 more at the Madejski Stadium.
London Welsh got their first win in Europe in Pool Five as they beat Cavalieri Prato 32-31. The home side emerged with two points after scoring four tries, but a brace from wing Joe Ajuma and another try from hooker Dan George allowed the Exiles to pick up the major points.
Having led from the 11th minute, when George crashed over for his try, Lyn Jones' side then conceded two quick-fire tries in the space of six minutes to lose the lead for the first time on 76 minutes at 31-29, but full-back Alex Davies stepped up to fire over a 45-metre penalty two minutes from time to clinch the win.
However, Stade Francais remain top of the pool after beating Grenoble 28-25 for their second win in two outings.
Under a deluge of rain, Stade Francais needed Felipe Contepomi to covert a late penalty to snatch the win, having found themselves 25-15 down at one point.
Bayonne put themselves on a collision course with Wasps in December for the leadership of Cup Pool Three after making it two wins out of two with a 22-19 win over Newport-Gwent Dragons at Rodney Parade.
Outside half Benjamin Boyet kicked 17 points as Bayonne backed up their 71-7 defeat of Mogliano in the first round.
The only other points came from a first half try by skipper and second row Mark Chisholm.