2001 7.3 last winter and start of this winter,win cold starts great but has sucking noise like vacuum leak. on road makes noise, same noise like turbo sucking,loss of power,let off pedal or hit brakes noise and power return. when its warmed up turn off ign and restart problem goes away,have checked for vac leaks and fond none, no codes on pcm, think its exhaust bypass? confused at time of year and just starting, owned truck since 2002,125,000 miles. runs great except for above issue. thanks for any help. new to site and love it.

 

Probably the exhaust back pressure valve mine does it also

 

Let it warm up longer and see if it quits. Jstewart is right with the EBPV.