D'Souza triggered a day of upsets as I V Rajeev of Andhra Pradesh stunned Manan Chandra of Petroleum Sports Promotion Board 4-1 in Group M and Rajat Khaneja of Chandigarh shocked Ashok Shandilya of Railways by the same margin in Group P.
Defending champion Shahbaz Khan of PSPB struggled for the second day in succession as he laboured to a 4-3 win over Aayush Kumar of Punjab after leading 3-1 in Group A.
In a match of fluctuating fortunes, young D'Souza fashioned his second win in as many ties in Group B as he rallied from 2-3 and defeated Bhopal-based Chawla to enhance his hopes of qualifying for the knock out round of 32.
D'Souza trailed 1-2 early in the best-of-seven frames contest but snatched the crucial fourth frame on the black before forcing the decider.
Other important winners were sub junior national snooker champion Dhwaj Haria of Gujarat, Maharashtra snooker number one Hasan Badami and Group K and Pune-based dark horse Yogesh Sharma, who fashioned his second win in as many matches.
Among women, defending champion Chitra Magimairaj of Karnataka registered two wins in as many ties in Group A, while former national snooker champion Anuja Thakur-Chandra of PSPB and 8-Ball national champion Neena Praveen of Tamil Nadu scored their second wins in their respective groups. (MORE)