you should tune PID for a tighter wg and this aint doin with a cat. wiki covering thats pvdksdk things and with proper tune even on a small turbo (btw is it stock one?) and 14psi wg you can achieve great results with wot and partial throttle
and check your fueling. idc 100% @3k wtf?
Yes, stock turbo (going to change for gt2871r soon).
I think 100% idc is because of icy roads and a "lot" of wheel spin when accelerating (stock injectors, now they´re changed)