A local lad up here has a Cat Back and Carbonio on his K1 and runs Stage 2 based on Revo recommendations. Not sure what the setttings are.
He is however looking to add on the intercooler, pump and downpipe as soon as finances allow.
I was always under the impression Stage 2 code allowed for uprated components, ie more efficient air in and air out and higher revs, but I guess this is maybe not the case as you still run the stock intake do you not Ben?