Ok, so Prime tested everything and couldn't find anything wrong and could only recommend replacing significant amounts of wiring which just isn't worth it on the car imho, especially since we have no clue if that's actually the cause. So they replaced the o2 sensor and came to the realization that the one cylinder was showing high roughness (which I pointed out was known since the build, Demetri actually had me monitor the roughness after the build but it had gotten worse). So they pulled the injectors and sent them to ID for servicing. Going onto my second week of a rental which stinks and makes this all the more costly. Ah well.