550 tire pressure/squeeling

Does anyone know the proper tire pressure front and rear for the standard michellen pilot sport tires on the 550? My manual says 29 psi frt and rear, but the tires tend to squeel under fast & moderate, tight turns.....It doesnt take that much really....
The tires look to be in fairly good condition, good tread and so-forth...it also has the barchetta modular rims (if that makes any difference?)...but tire sizes are standard as per the manual.
I would really apprciate any insights/leads regarding this...its a little sad sounding squeeling your tires taking a simple turn at moderate speeds...not very Ferrari like!

 

I would generally agree, if I was pushing the car to extremes....but in this case, I am not....my ML500 takes a comparable turn with more silence, albiet more body roll...