4540 vs 4550

[truckinfouble]

Is the only difference the Engine Control Module? Or is there a difference in the fuel pump pressures?

 

[truckinfouble]

Well, looks like either nobody knows, or if they do they are not telling lol. In an effort to solve this puzzle could someone with the 4550 please post or message me the part number for your ECM (its behind the kick plate under the steering) and the part number for your fuel pump? Just the part number and not your serial number. One or both hold the key to unlocking 8 HP