Oh OK, am I correct saying it's fuel pump speed?
I took the fuel pump out and have found that it is a GTR fuel pump. Yes the sputtering is a new problem, was tuned when I got the link fitted. The tuner mentioned it kept blowing coilpacks, so they asked me to either go ahead with the R35 GTR coilpack conversion with new harness, as it ran better. Since having it back a month or so, it slowly started to develop this problem, it's when it warms up and the sputtering/missing gets worse as the engine gets warmer. I turned it on the other day and it was sputtering from a cold start as well.
I was told buy the tuner, to check all my earth's and loom. I cleaned all the earths and nothing. Loom is abit harder as I'm pretty sure it's an engine out job. I unplugged coilpacks on cold, each one made a change to revs, when it with the issue, I unplugged them all and cylinder 1 and 3 didn't make a change. With that fault, I thought it might not be getting enough fuel.