ok i had the code p401 the egr insufficent flow code, so i read up on the forums and came to the conclusion to clean the egr n then some.i cleaned my egr valve (the 2 ports), i cleaned my intake manifold, i took off my throtle body and cleaned the crud out of that, put it all back. double checked all the vacum lines n plugs. now its running like shi* it stalls and when its not stalling it idles so bad it makes me sad. all this work to find it running like crap. any ideas, from what i can tell no vacum lines, but there is a buzzing sound coming from my pasenger side. ( its the thing with the 2 little L shaped plugs going to it and the electrical connecter above that, its black.) i am angry at my truck.

 

Just guessing here but did you clean the IAC? It controls the idle (Idle Air Control). On a 5.4L it's on the back side of the intake manifold up against the firewall.

 

yes i did clean mine, mine is right behind the throttle body, on top of the intake manifold.

 

My 4.6 would start good but die if you let up on the gas. I cleaned the IAC and that fixed it for a short while. The same problem returned and I replaced the IAC all together. It's been six months or so and no more trouble. You may need to replace the IAC. Some times cleaning it won't do.
P0401. The ports you cleaned were in the elbow at the EGR Valve correct? They should have been full of carbon. P0401 is very common.

 

Could just be a bad DPFE sensor causing the code.