Lancer Buzzing

ill post it for a second time since we had a problem with the forum and my thread earased.

since ive installed my headers, downpipe and testpipe, there was a buzzing when i was reving the car and it was really anoying. i tought it was a leak in the cheap headers gasket, ive got one from the dealer and installed it last night and it still doing the noise. we looked better to see where the sound was from and it looks like it comes out of the intake... i tried another filter (weapon r foam) to see if this was the problem and it still doing it...
I think maybe it because of the manifold, the engine takes more air in and out the engine, but i dont have my catback yet, im still runing the stock catback so maybe the muffler make a too big restriction and the noise come from there???
maybe Brent can answer that for me..
im ordering my catback tomorow so i hope its gonna fix things...
Thanks
Remi
P.S. im not that good in english so its kinda hard to explain...