Heat really helps them........ Very short downpipes.. and a large air filter ... So a turbo blanket will hold the heat and keep them spooling .. Just put it on the back of the truck and 3600 stall with 3.42 gears and they will hear you for miles... LOL ... kidding.......

 

Get a whistle tip...

 

Get a pair of vise grips and pinch off the oil feed. It will get real loud, real quick...

Short, big diameter downpipe without a muffler will make it sing all the time.

Rick

 

From my understanding the turbo is louder caused by the compressor inlet. Just like the pic. The shroud is why the turbo is louder. The air has a swirl like affect creating a whistle...