code 1131 and 1151

[69machrk]

okay got these codes, so far i did a tune up,plugs,wires, fuel filter,air cleaner.... and cleaned the maf, replaced the intake gasket...... when i removed the pass. side rear plug it had fouled, looked to be running rich, the codes came back about 100 miles later....... think this could be the injector going bad ? 2000 ford ranger 4x4 4.0 auto 4:10 gears

 

[cr_the_machinist]

How well is it running? Any sputtering or surging?

 

[69machrk]

when i first start it up its fine then after about 5 min. while driving it feels like its running out of gas,i can keep pumping the gas and it comes back to life and is fine the rest of the day, on the highway it starts missing at about 70mph, not real bad but you can tell it again feels like its running out of gas....... fuel pressure at idle is around 45psi