Union Comercio edged San Simon 1-0 away from home on Friday, while champions Universitario came from behind to beat Cienciano 2-1 on the road on Sunday.
Both teams are two-from-two after the opening rounds, but Union Comercio (+5) are ahead of Universitario (+4) on goal difference.
Union Comercio came into the clash on the back of a resounding 4-0 win against Los Caimanes last week and they were expected to get the job done against San Simon at the Estadio 25 de Noviembre.
They were forced to wait until the final 13 minutes to claim the points, with substitute Antonio Meza Cuadra the hero for the visiting team.
San Simon ended the match with 10 men after defender Jean Rodriguez saw red for a second bookable offence in the 81st minute.
As for Universitario, two goals on either side of the half-time break saw them emerge triumphant against 10-man Cienciano at the Estadio Inca Garcilaso de la Vega.
Gary Correa had given Cienciano a 25th-minute lead after finding the back of the net with a sublime free-kick.
But the visitors eventually hit back through Raul Ruidiaz, who was on hand to tuck away a rebound on the stroke of half-time after a swift counter-attacking move.
Universitario completed their comeback just six minutes into the second half, when Christofer Gonzales let the ball bounce before firing a volley into the top right-hand corner.
Cienciano were dealt a blow in the 66th minute following a red card to Fernando Masias.
In other results, Carlos Gonzales scored twice as Inti Gas moved up to third in the standings thanks to a 3-1 win over Sport Huancayo on Saturday.
Inti Gas have four points, the same amount as Alianza Lima, Cesar Vallejo and Melgar.
Alianza Lima defeated Real Garcilaso 2-0 on Sunday, Cesar Vallejo netted two first-half goals to beat Juan Aurich 2-0 on Saturday, while Melgar were 2-1 winners at Sporting Cristal thanks to Ysrael Zuniga's late brace on the same day.
Elsewhere, Los Caimanes and UTC Cajamarca played out a goalless draw on Friday and Leon de Huanuco equalised five minutes from time as they drew 1-1 with Universidad San Martin.
