hi guys i have a 97 F-350 4x4 crew cab 5 speed manual ZF5,just put the 3 inch downpipe on it and into 4 inch straightpipe,i cannot hear the turbo whistle and does not spool up,I have another 97 same pickup same setup only difference is it has the auto tranny,this one you can definitely hear the turbo.The 97 with the 5 speed i just put a used engine in it,could it be a bad turbo?vac leak?any ideas?

 

If you have the stock air cleaner on the truck, you will not hear the turbo spool up just sitting and revving the engine. It needs to pulling a load, or working the engine pretty hard, then you might hear it.