The flickering is intermittent, some days it'll just start happening once it's fully up to temp, others it'll be absolutely fine. I don't think it's the oil pump on it's way out, as the engine was fully rebuilt a few months back I've been told it could be the BOV, apparently it can confuse a few of the sensors if it's exhausting too much to the atmosphere at low revs, which can cause rev dropping (and in worse cases stalling)... Gonna look into changing all the sensors and if that doesn't fix it, a brand new BOV could be happening (which I'm secretly hyped about because I get to rid myself of the cheap one on there already)