I acheived this effect, BY ACCIDENT, on my rig with duall 8" straight pipe exhuast. I had tore the modified tin can I called a muffler out from underneath on a off road construction site job, and when I replaced it, I installed the thing backwards. It had a perforated internal cone it it, and holy crap, did it whistle !
I went to work the next day, unknowing the issue, and all day long, whenever the turbo would spool up, it whistled like a screaming banshee...
I did fix it that evening, though. No more woot wooot for me. NoWhaImSayin!!!