I have searched this over and over and cannot find anything on it.

My truck has a momentary moan / growl / bog down issue. It happens at town and highway speeds and usually when I have cruise on OR when I lightly apply the gas peddle. It moans for a few seconds and seems to bog down then comes out of it and carry's on its way. You can hear it plainly while driving even with radio on. I have a regular muffler on the truck but when this happens, it makes it sound like I have a catback on it.
Things i have done...HELP this is getting annoying!

new air filter
new oil/filter
new fuel filter
ran techron injector cleaner through tank of gas

 

Might wanna yank the throttle body off and give it a good cleaning while you're in there. I hear it does wonders for these things and can often fix that weird growl.

I get it too on mine -- I haven't had time to yank the throttle body off. I'm sure it needs cleaning after 146K miles. It also improves response times of your foot cause the motor controlling the butterfly gets all gunked up and doesn't wanna respond quickly.

This is all heresay -- I've not done it myself, but read several times on the forums thats what causes it.

 

I cleaned it about 10000 miles ago, I will give it a try this weekend and see maybe it will help!

 

I have the very same issue... My 165,000 mile, 2004 F-150 is currently at a transmission shop today in hopes of diagnosing this very annoying problem. The growling started to be only on very hot days, every once in awhile and now, 2-3 years later... It does it all the time. The interesting thing is that bumps in the highway will make it start the deep bellow / groan and bumps in the highway can immediately cease the loud groan. I have repalced spark plugs, cleaned every sensor, cleaned the throttle body, etc... Still searching for the culprit....

 

And there has never been a check engine light up and no codes with a scanner...

 

Assuming you have a stock intake, check the lower side of your air filter tray for a foam gasket at the bottem edge. If it is missing or worn, replace it with more foam or even weather stripping.

Your problem could be this as more air is getting into the motor.

 

Would too much air getting in cause the gas pedal, throttle, to become non-responsive? In order to quickly eliminate the noise and regain full power, you have back off of the gas and then roll back into to the throttle...