Steering Help, wife gonna kill me

Hey folks have a situation with by '97 k1500 it has the ever present issue with the elec. box that monitors speed that determines amount of power steering needed (don't know the name of it). Any way I've been putting it off....until now, the wife was driving home for the first time with the new rims and tires and almost hit several vehicles luckily god was watching over her, so inorder to keep my hide intact I need some help.

Has anyone heard of the tire width exagerating the problem I just went from 275's to 305's, the wheel diameter is rough the same, variable by an inch perhaps 2. second question am i in need of some sort of stablizer shock or a bigger one rather. Last but not least per a mechanic friend of mine the "speed/steering box" also needs calibration?? Was unaware of that. Thanks in advance to all including the occational heckler =]

Take a look at this thread: http://www.automotiveforums.com/vbulletin/showthread.php?t=229834

//2000CAYukon