keeping different pressure in front and rear tyres does not make the car unstable(there myt b exceptions though but not on our local cars)..
recommended pressure is given on pillar ...thats mostly for when the car is loaded and you can take out 1 or 2psi when driving local without full load..
having +2,-2 psi can change the whole driving experience believe me..
underiflated and overiflated tyres sure are dangerous and may blow up...
if you take out -2 or 3psi from what you normaly are used to..you will notice smooth drive with fewer bumps and you will feel grip while u drive slow but overall the car will feel slughish and will not respond crisply at all..at high speed this is more probable to lose grip on turns..(and underinflated tyre regain control later than what you would normaly expect if it loosed grip{i read it somewhere})
having +2 or 3psi from what you normaly are used to will give you differentiable hard and rough ride..although drive will be crisp..will not grip when you push the car hard
the bottom line is...the tyre pressure can be changed by +3 or -3psi from what you will find at the pillar..it depends upon personal driving preference and would not effect the tyre
but increasing or decreasing these psi number by much difference might even blow ur tyre...for example is saw it on bbc long time back some wagon towing very heavy machinery and they put in bags full of mud and inc the tyre pressure to very high extent but then the car could be driven til 10mph ..increasing would result in blow out
