98 buick century p0306

Hello i have a 1998 buick century with 3.1 motor. The car has sat here for 3 years without being used. It ran great when i parked it 3 years ago. Now i'm trying to put it back on the road but its running poorly and giving me a code of p0306 on my scanner. It idles ok but if you accelerate in neutral it stumbles if you try to drive it is much more noticeable under load the hole care shakes. I have changed the plugs/wires and fuel filter and it hasn't improved. Im wondering how you go about testing the fuel pressure and how to check the coils with ohm meter ? any help would be greatly appreciated i cant afford to throw many more parts at it.

3 years? Fuel gum up on the lines. I am pretty much sure the injectors are plugged up. Pour a bottle of Techron is about $12 in Auto Zone. It says to run it with a full tank of gas, I would say, 1/2 tank.

When you store vehicles for such a long time, the fuel system has to be purged of fuel. Including the fuel tank.

I do not think is electrical. On the 3.1 has a vacuum system or 3 lines or so, make sure they are not rotted or cracked. EGR could be stuck partially open or close but I do not think that is the issue.

Good luck