2000 GMC Sierra Z71 having problems

[Jay-Z71]

Hey guys I have a 2000 GMC Sierra Z71

Having trouble getting it to run right

The truck had been parked for about 3 months cause the fuel pump went out

But I replaced it

And got it going then a couple days later it started running ruff so I changed out coil packs, wires,and plugs and the fuel injectors

It started up and drove perfect

A couple days later I noticed it started idling a little ruff

And the check engine light started flashing

So now I'm a little stumped on what it could be

Any help is appreciated!!

[txab]

Check stored codes

[Jay-Z71]

I'll check out codes and post em

[intheburbs]

Flashing CEL is a misfire. Check your plugs and wires.

[sahls01gmc]

Did you change the fuel filter when you changed the pump?

[Jay-Z71]

Yea fuel pump and filter were changed as well

Here are two codes that popped up

PO307 Cylinder Misfiredetected

PO141 O2 Heater circuit(Bank 1 sensor 2)

I pulled out the plug from cylinder 7 and it was really dirty and I just replaced them last week

[traxxas5308]

check the wires on your passenger side down stream 02 sensor, if it all looks fine then you just need a new o2 sensor.

[Cosmic Charlie]

Rusted Grounds ?

Air Filter filled with Animal Nests ?

[Jay-Z71]

I changed out the o2 sensor and changed the spark plug

but nothing helped so I checked the wires and coils everything is good so

I'm thinking the injector was a dud

Or something cause I bought all 8 new together

[Daryl LBZ]

Could still be a coil pack going bad or already bad...

[Jay-Z71]

That what I thought it could be too but they are brand new

And I swapped coil packs from another Cylinder

To see if it made a difference but nothing