I have an 03' F150 XL with the 4.2L and I've recently had sputtering when I accelerate. I've had codes pop up, first it was a misfire on cylinder 3 (about 3 months ago) and it went away on it's own. Then about a month ago the sputtering came back and so I put in new plugs and wires. Seemed to have fixed it but it has come back and it's spitting codes P0171 and P0174, running lein on bank one and bank two. I've changed the air filter, cleaned the MAF sensor, checked for a vacuum leak and cannot find one. and now the sputtering is random, it's a calm idle and calm up to about 35-40, then the sputtering starts, exhaust sounds like a lawn mower. (Also I have a flowmaster 40 series with a side exit right in front of the passenger side rear tire) the sputtering will continue until about 70 mph on the high way, then it cuts out. But then as soon as you start up any sized hill on the highway the sputtering comes back and it almost seems as if the transmission is slipping. Any insight, or help? Thanks!!

 

You have 1 possibly 2 troubles at the same time.
Address the missing first to see if this stops the misfire.
Remove the vacuum hose form the EGR and take it for a drive long enough to see if the misfire is gone.
If yes, the intake has to come off and clean the EGR ports inside.
Clean the EVR solenoid to be sure it's not sticking open.
For the 171/174 codes there is an air leak your not finding.
Often on there motors the intake manifold sealing has an issue.
There could be rubber parts on the intake failing as well.
If you find removing the hose from then EGR stops the misfire you will have to remove the intake anyways so solve both issues at the same time.
Good luck.