2008 F150 PO308 and P0174

Working on a 2008 Ford F150 4.6 throwing a bunch of misfire codes and running real rough. Codes thrown P0300, P0301, P0303, P0308 and P0174. Truck does have over 200k miles and we've changed all 3 of these COP's on these same 3 before. Changed COP on 1 and 8 cylinder because the day before it threw those 2 codes. Still rough and misfiring. Codes thrown still for 1 and 8 cylinder. Pulled spark plugs, 3 had Autolite platinum and 8 had Motorcraft copper. Changed both to Motorcraft platinum. Still rough and misfiring, but only on number 8 cylinder along with the P0174. So number 8 cylinder has a new spark plug and new coil over plug. Checked for any cracked vacuum hoses especially the PC valve and they looked good. Hooked up my smoker from the brake booster, nothing. Then hooked it up at the test port on the passenger side, no smoke. So the intake manifold is good. The ONLY thing left is the fuel injector. Replaced just the one fuel injector on number 8 and she's purring like a kitten! Hope this helps someone! Thanks for watching!