TCP is the most widely used transport protocol originally designed for wired networks. But many experiments have shown that its performance is poor when used in wireless networks. Also improving its performance in wired-cum-wireless networks preserving the end-to-end nature of TCP is a difficult task. To address this issue,several new protocols and TCP modifications have been proposed. Snoop is one such modification. But it can not be used in isolation but has to be combined with TCP. Whenever Snoop is added to TCP Sack or TCP Reno, the performance of the TCP Sack or TCP Reno is observed to be deteriorating when compared with the performance of TCP Sack or TCP Reno alone. This paper analyzes the distinct behavior and introduces a modification to the Snoop protocol for wired-cum-wireless networks. The modified snoop protocol improves the performance of TCP SACK by around 10% compared to the plain TCP Sack protocol and 5% in an environment where no TCP enhancing mechanism is in place. Theperformance of TCP RENO is also improved by 30% compared to the plain TCP Reno protocol and about 20% with no TCP enhancing mechanism used.