A GT3 front bar will NOT help this situation and neither will tire pressures. The GT3 bar on full soft is not softer than your stock S front bar, so what benefit do you think will be gained by going to one? You need more front grip. That is the bottom line.
You can do any of one of these.
Decrease front spring rate
Decrease front anti roll bar rate
Increase rear spring rate
Increase rear anti roll bar rate
Run the car square (same size front and rear tires)
I make changes in 25lb increments with springs until I get the cars dialed with the front GT3 anti roll bar set in the middle and a 4 way Tarett set on second from full soft. You don't have the rear anti roll bar option or the easy option of changing springs out. So.. remove a front drop link and drive the car. This effectively removes spring rate from the front of the car and will make the nose turn in and the rear feel loose. This costs you NADA
Tire pressure changes only effect the car in a couple of LB's of spring rate. You need a big change (Course adjustment) then .. then fine tune with the tire pressures.
If you were close to me.. I'd show you in 15min how this is all done, with a single clover leaf highway on/off ramps
B