milhouse200sx

I just got a stillen muffler, 2in piping, and hotshot header put on. When the rpms go past 2500 it lets out a loud screaching sound. My friend told me it will go away after you burn it through. I have had it on for like 2 weeks and its still there. Does anyone know what this is? I just want a deep tone to the exhaust. Thanks.

James

did you put in a glass pack behind the cat? it helps with misc. sounds coming out of the exhaust.