Yes all 4 injectors are low impedence, and they are all going through a FJO injector driver, before they reach the ECU.

Also, could you explain how timing can cause this problem... I'm having a hard time understanding :(

I can't remember which way mine was off, but it would hit a wall at like 3.5 grand. spin it the other way and it would stumble and bog.

set the TPS first, then set the timing or it will be off. make sure you're idling at 750-800rpm and the car is fully warmed up before attempting either.

if the car was running fine the only things I can think of are the injectors or you caused a vac leak when you removed the manifold. only use OEM gaskets and zero silicone.