You said you ran the pipe 25 feet BUT you didn’t mention the trap for the shower or how far away is the vent from the trap?
Instead of calling a rooter guy WHY not call a Licensed Master plumber as NO ONE knows more about “Proper” venting or drainage than a plumber.
What you did describe sounds like a HIGHLY ILLEGAL indirect waste hook up. Any 1st year apprentice would also know SNAKING does not remove odors AND chemicals most of the time cover up the smell by adding another type of smell.
Call a REAL Licensed plumber and ask them about water jetting the pipes clean to a like new condition removing all the old soap scum build up that causes bacteria that in turn causes the smells. Call the RR guy and ask for your money back. Good luck
[Edited by SylvanLMP on 08 June 2000]