Momanyi, who joined Gor Mahia last January, powered home late into the match to help Dylan Kerr side pick maximum points in a 3-2 victory over the Mike Mururi side.
Ephraim Guikan hit a brace in either half, but the Ivorian needed Momanyi’s late winner to steer Gor Mahia to victory.
Kerr, who has another tough assignment against English side Hull City on Sunday, had to gamble with his squad when he opted to field a second string side for the mid-week match.
The gamble, however, paid off, but with a little scare, after Homeboyz took the lead mid in the first half through Ali Bhai.
Ivorian import Guikan restored parity for the reigning champions with two minutes left to the breather before doubling his effort 10 minutes after the break.
Former AFC Leopards and Tusker striker Allan Wanga brought Homeboyz level in the 70th minute, but Momanyi rose to the occasion with an 80th minute match winner to save K’Ogalo from the brink of another draw.
Gor Mahia have now opened a five-point gap between them and second-placed Ulinzi Stars. Gor Mahia have two games at hand.
Kakamega Homeboyz XI: David Juma, Hedmond Mauda, James Situma, Moses Chikati, Smith Ouko, Esion Esiye, Ali Bhai, Kiyoyo Hassan (85' Andrew Kulecho), Moses Mudavadi, Noah Wafula (70' Festo Omukoto), Allan Wanga.
Subs: Michael Wanyika, Anekeya Wilson, Evans Kiwanuka, Andrew Waiswa and Collins Odhiambo.
Gor Mahia XI: Shaban Odhonji, Charles Momanyi, Joachim Oluoch, Wesley Onguso, Innocent Wafula, Lawrence Juma, Kevin Omondi, Cercidy Okeyo, Boniface Omondi, Samuel Onyango and Ephraim Guikan.
Reserves: Boniface Oluoch, Harun Shakava, George Odhiambo, Francis Kahata, Jacques Tuyisenge and Meddie Kagere.