Alwanga has scored three goals in 13 appearances this season.
Harun swept home from his first goal for the club on 35 minutes.
The result takes our tally to 34 points, two behind leaders Sofapaka.
David Okello starts in goal ahead of Allan Owiny who is out injured.
Mathare United won the first leg 2-1 in Nakuru.
The result leaves us fourth with 31 points.
Club top scorer Cliff Nyakeya is back from a one-match suspension.
This will also be the first time Situma will be playing against Homeboyz at Bukhungu since leaving in June.
The result leaves us second with 31 points.