You did get one step colder plugs didn't you?... And check your belt just to see if it might need changed

 

Did you replace your wires? I developed a noticeable stumble after putting in a 15 % pulley even with new plugs and a new coil. Once I replaced the wires, smooth as silk.

 

Yes. One-step colder plugs were installed.

I didnt replace the wires. They literally look like they are brand new, inside and out.

Car has been doing better actually. No more stumble, boost seems to be hitting 16psi (still slightly creeps up to 18, but a lot slower) and hasn't thrown a CEL or code over the last couple days of heavy driving (crossing fingers).

Thank you to everyone for your suggestions and advice in regards to solving the problem. Looks like plugs were causing a majority of my issues. For reference, the plugs I pulled out were E3's; they were not fouled or damage in any way cosmetically. Who knows.