Nistune woes

I'm going to be honest, this is a noobish question. Probably cut out for the basic-mods section, but on with it.

I'm aware nistune is not plug and play by any means with a stock tune and a modified K value.

But so far my K is around 320 and my latency is around 1000. Timing is set at 10 and Nistune confirms.

The problem is that the tune never seems consistent. When fully warmed up, the Z will run rich.
Around 12.5 AFR idling, 12-13 cruising and 10-11 at 7psi boost, richer with throttle position. But
suddenly the tune will change and the idle will be around 14.5 which is where i would want it, cruising is around 14
and any amount of boost, the AFR's stay around 15-15.5.

The tune is permanently burn so it's not a temp file. It's almost like it switches maps. Making tuning impossible.

Any ideas?

EDIT:

My setup consists of a 255lph, 420cc injectors at stock fuel pressure, Stock MAF, t4 turbo at 7psi, intercooler, vg33