The pressures needed to completely overcomee understeer you don't want to run day to day. I always run ~ 3-6 lbs more front than rear- depending on tire and application. This will help a little. I use springs/alignment/sway bars to really alter handling balance.
What the D Stock guys did was run excessive rear presuures- like 50+ lbs. This effectively eliminated much of the grip of the rear tires allowing them to rotoate their cars better-the reason they did this as they could not alter rea sway bars/springs/alignment (only as far oe equipment would allow). I would not suggest this for the streeet.
You can dial out understeer w/ larger sway bars rear/smaller front;
increasing rear spring rates/decreasing front; more neg camber up front/less rear;
increase damping rear/decrease front (adjustable dampers obviously)- these are generalizations and each component effects the other. It takes some work to get a neutral handling vehicle.