Hi all, only happens when not on the gas, typically heard at under 25mph. Makes me think of a vacuum link? Oh yea quiets when braking(using vacuum for booster?)???TIA!I checked pcv valve and what not...I do try to keep everything working well too...

 

It probably is a vacuum leak. Start the car, pop the hood and listen to see where the leak is coming from. They're sometimes difficult to find. It might be something as simple as your intake coming loose.

 

ya know...never thought about the upper plenum? didn't here the stupid thing today while listening for it! I did the headgaskets on it a year ago or so...

 

Did you replace the upper and lower intake gaskets when you did the head gaskets? I hope you bought all new ones, if not, there's your problem.

 

Yes, also replaced WP, plugs, filters, ign.wires, fluids,tires,brakes,whl.bearing, fuel tank...what else

 

Check all your EVAP lines, EGR, throttle body gasket.