MSBDX

Hey i was just wondering if anyone had this same problem or could tell me how to fix it. I have a 98 civic DX i have short ram intake , airmass 4-2-1 header, test pipe , greddy cat-back exhuast. When ever my RPM's get above about 3,000-3,500 the exhaust starts to have a crackling noise almost like there is water in the exhaust system and i was just wonding if it could be becasue i dont have a cat. If anyone can help id really appreciate it. THANKS!