P0305; 1999 Dodge Caravan 3.8L; stumbles during accelleratio

The MIL light has been coming on, code is always P0305. Van is at 32K miles, replaced plug and wire set at about 25K a few years ago, while doing the second serpentine tensioner assembly. I see that cyl 5 is on the rear bank, haven't gotten a hand back there to see the boot is still seated. I have gathered parts to replace plugs and wires again, but am also wondering about injection, after doing some online research. This Grand Caravan 3.8L did not have the Fuel Rail recall done, has mostly been run on Costco generic regular unleaded, with a quarterly additive of Chevron injector cleaner. Should I worry about injection, or just do the plugs and wires and see what happens? This AWD van is parked most of the year for low gas mileage, but is my daily driver during winter ice and snow. I'm late getting around to dealing with this, would appreciate any thoughts, as I will need it in the next few weeks.

injector not likely, use the correct champion brnd plugs and good quality ignition cables, at almost 9 years old they're likely junk!