hey i am also having the same problem but mine is kinda intermittant and from what i understand have read and have replaced im pretty much down to the fuel pump control unit on mine bout to replace that and i did that exact same thing you did as well with the plenum pull for the injectors to 555's and so o whats funy is i also had to replace my iacv with a used one bc i broke the blue end off the sensor lol so im starting to wonder if switching to larger injectors is causing the fpcu to fail since it is used to smaller injectors hence less fuel pressure needing to be supplied to maintain the proper pressure compared to the larger injectors that put more fuel in faster at higher hp and rpms ? just a thought let me know what you find out hope i help at least to clarify
