A 444 at 3000 RPM is drawing in 385.4 CFM.
But the air coming in is at say 50 degrees.
When it goes out the exhaust it will be somewhere between 300 and 1100 degrees after combustion. I dare say the the exhaust is almost twice the CFM you are drawing in.

If you ran 385 CFM through a 3" pipe you would have a flow speed of about 90 MPH.

 

i have a single chamber delta flow on my 7.3 sounds good ran a 2.5 y of the back of it in to 3.5 tips and the thing sounds great. not real laud at idle nice deep sound then when u get on it it rumbles like no other. i figured every budy was running the 40 series so i wanted diffrent and boy am i glad i did this thing has a 6" long case with a single v baffle. wish i put it on sooner i was just running a cheap autozone glass pack befor sound pretty dessent exspecally when i was letten of the peddle it cacalled pretty sweetlly. my advice keep trying till u get the sound u like. thats what i did and it works well. pluse its fun.