Sorry about that chef, I saw the 260RS in your profile.
The upgrade path is pretty straightforward I reckon a hi-flow is probably the most logical step as there is the least time messing around.
GCG hi-flow, Hypergear Hi-flow, HKS GT-RS, HKS 2835ProS, GT3071, GT3076 are all options each with its own pro or con either based on price or result. Some will need additional parts like dump changes, spacers etc.
I may have a HKS GT-RS kit 2nd hand for sale or a HKS 2835 ProS kit (with a brand new cartridge installed) once I decide which one to keep.