Want to add a few things about tire pressure.
As most know over inflation or under inflation will effect tire wear. Over causes the center to wear first and under causes the outside to wear first.
Under inflation also causes the steering to be sluggish and increases the chances of the tire rolling under. However, it usually helps soften the ride (if your into that).
Over inflation does help sharpen the steering responses, but it also makes tram-lining (following road ruts) worse and makes the car less stable in cross-winds. Of course it stiffens the ride quality too.
Both over and under inflation increases tire temperature when driving. This good be a good thing or bad thing depending on the tire and the road temperature.
For instance a high performance tire likes to be warm. But a winter tire can become very squirrelly when too warm. At extremes the tire can fail due to a combination of high heat and pressure.
My opinion:
Personally, I like to go no more than 7 PSI above and 4 PSI below recommended pressures. And I like to have no more than 7 PSI difference between front and rear. Except for AWD cars, where I think keeping all 4 tires equal is best.
On my WRX I have 33 PSI all around. On my M3 have 35 PSI front and 39 PSI rear.