Intermittent rough idle

97 Ram 360, When the rough idle starts you can here what sounds like a major vaccum leak around the throttle body area. Idle will return to normanl and at the same time the noise disappears. Also on occasion when accelerating on the highway the truck will have no power and backfire and sometimes it feels like it takes alot of effort to maintain 55 like something is holding the truck back. Please Help, Thanks in Advance

97 Ram 360, When the rough idle starts you can here what sounds like a major vaccum leak around the throttle body area. Idle will return to normanl and at the same time the noise disappears. Also on occasion when accelerating on the highway the truck will have no power and backfire and sometimes it feels like it takes alot of effort to maintain 55 like something is holding the truck back. Please Help, Thanks in Advance

Check the vacuum hose to the brake booster and also check/replace the PCV valve and hose.

I had the pre-cat O2 sensor replaced and this seems to have solved the problem. Thanks for the help.

Glad that fixed it; if you keep hearing the leak, you may have a failed plenum gasket. (See the numerous posts here on it)