2003 wont start

I have a 2003 Century that died well driving and would not restart.
The car was towed home.
The car will kind of start now. If you keep you your foot on the gas. Kind of stubles and will stay running like this for a few seconds.
There is an error code P0300
I pressed the valve on the fuel rail and the gas sprayed out. Tested for spart on the front 3 cyclinders and had sparks on all three.
What else can I test and any ideas?

You need to actually test the fuel pressure also, if it has a maf sensor disconnect it and see what happens.

Like Max says, check fuel pressure......also check for spark on the back three plugs.....check for injector pulse......

Rented a fuel pressure gauge. It was just under 60 seemed a little high but not that much.
Unpluged the MAF sensor no change. Checked the fuel pressure regulator does not seem like gas in the vacume line.
Did not test check for injector pulse not sure were to do it at. I see the fuel rail but I do not see any electrical connections. Do I need to pull the top intake off?

It kind of seems like it is flooded because IF you do get it running it is with my foot on the floor and it spitting and sputtering.
Thinking I may need to pull all the plugs and see if one or all are wet.
The problem is the plugs do not want to come out. The car has 250K mile and I do not know if they have ever been out.

There is a bulk connector coming out of the upper intake.....that is the connector for all the injectors......disconnect it.......you check for injector pulse there at the harness(need a wiring diagram).....can check the injector resistance on the other half of the harness with an ohm meter....should all read about 12 ohms......

With the harness disconnected, crank the vehicle several times.....this should dry out the plugs........then with harness disconnected, see if vehicle starts by having someone crank vehicle while you spray carb cleaner into the intake.....

250K and never changed the plugs? That would be the first place to start.

250K and never changed the plugs? That would be the first place to start.
I would definitely spray them down with some type of penetrating oil, not WD40 but something like PBlaster, Kroll, etc. Hate to see you twisted one off in the head.

250K and never changed the plugs? That would be the first place to start.

I said I do not know if they have ever been out. I have not owned the car it hole life.
Plus I have never seen spark plugs make a car die in the middle of the road.
Update on car. Gave up and towed it to a shop. They looked at it and said they are 80% sure the timeing chain jumped a tooth or 2. They said they could fix it but not worth the $$$ with that many miles on. Good news they did not charge me.
Now car is at home again an maybe I will work on it maybe I will junk it. No time right now to decide.

To me, 80% sure means, it's a guess on their part, and they didn't charge you, because they did no testing...

To me, 80% sure means, it's a guess on their part, and they didn't charge you, because they did no testing...

Yes a guess but they did some testing. They Tested I know they tested at least fuel pump and coils. I did not bother to tell them I already tested these myself.