P1261 and 1262 after spark plug change
 

I changed the spark plugs on my car and in doing so seem to have caused some issues. Upon starting, the car fired once and died several times, only staying running once before I killed it due to a very rough idle. It sounded like it was running on 2 cylinders. My first thought was misfiring due to the new plugs however it does not seem like this is true anymore.

I pulled 3 codes from the car, P1261, P1262, and P0451. 1261 and 2 seem to be injector related, while 0451 is in the evap system. My guess is that because I had to move the ECU and turn it (nothing was disconnected), I may have created a wiring issue. However, I am unsure of how to test that hypothesis and am worried about damaging the engine.

I would really appreciate some guidance on what the issues may be and how to potentially diagnose them.

The car is a 2013 M/T FRS with Open Flash header and tune along with the Greddy intake. 60k miles.

I'd suggest you make sure the ECU is grounded good.

You nailed it! Thank you so much. The bottom bolt on the ECU is the ground and that was causing the issue.