First off you wasted the money on injectors. 2006 WRX came with blue tops rated at 565cc.
Second if you swap in a VF39 and tune it you will essentially have an sti with a 5MT.
If you run a Cobb Stage 2 Vf39 map, you will have a stage 2 Sti.
So what you are calling a Stage3 WRX = Stage 2 STI