Leif,RUSS-D SOMEONE HELP? WEBER PROBLEMS

Ok guys I put a weber on my truck off my buddys ride. I have the most aweful whistle I have ever heard and can not pin point it. I drove it and as long as the gas was pressed it did not whistle but when you dont have the gas pressed it sounds like a tea kettle on crack. Also when it idles it runs like pure shit. Any ideas? Anything I may have not done. The header is plugged off also. Damn mazdas my mighty maxs fuel injection is the shit. damn buy a weber to fix problems and i create one.