Hissing Stacks - HELP!
 

hey everyone..today i drove into work no problem but when i started the truck at night it was much colder out and i noticed a hissing noise when i accelerated...it starts out with a whistle then turns into a loud hissing..when i get on the gas it cuts out but when i back off the gas it starts again until i am moving slowly then it stops..any ideas on what this might be? i was thinking EBPV? - anything thoughts on how i can fix this or is it normal? any help would be great thanks guys! (also noticed after a few minutes of idling every once in a while it will idle a little higher like stepping on the gas on its own?!?)

Normal EBP valve operation.

yup.......

Might be water in your stacks.