So its a 2002 F-350. Only mods are afe stage 2 and MBRP 4" turbo back.
The noise started right after the exhaust. Only happens when the truck is started cold. It idles and sounds normal for about 3-4Mins then the banshee shriek from the tail pipe starts. I can rap the throttle once and it goes away and doesnt come back tell it starts cold again. If I take off driving as soon as it is started the noise never happens. Any ideas?