Multiple misfire now with DTC P0138

Hello everyone, I turn to this forum quite a bit, and it's been a great help. I've been trying to troubleshoot DTC code 3001 and 3004 for a while now. Decided to switch fuel injectors #1 and 4 with #2 and 3 to see if it changed on the one readout. After starting the car it was running very rough, hesitating, smoking a bit and error code p0138 appeared for the first time, then the same misfire codes came back as well. It smokes a ton! I shouldn't have messed with anything, but the flashing error code was just bugging me, so I had to. I'm pretty new to mechanics, any advice would be helpful at this point. Thanks.