1997 blazer ls 4x4

Since i got my blazer about 3 years ago the brake were never that good. If u smashed the brake it will stop but needs alot of effort. Today i was drving and when it was cold the tires would lock up. abs would kick in once and while but when id would be coming to a stop the right rear and right front would lock up a lil more the rear. Once it would get warm it would go away but so would the sensitvity on the pedal. Some GM's i have drove u just tap the brake and you better hope you have a seat belt on. Other like mine theres really no sensitvity and mines getting worse. http://www.automotiveforums.com/vbulletin/showthread.php?t=556583&highlight=brakes i looked at this. I do have a hissing brake pedal when i press it down so a possible brake booster problem could exist. Is there a way to test it or is a hissing brake pedal the test for that. Also i had the front rotors cut and new pads, and new shoes in the rear a year ago. Im gonna roatate my tires this weekend and im gonna look at the brakes. What should i look for? or what could possible be the problem im having


and is there a way to bring the sensetivity of the pedal up a bit. I like a touchy brake pedal or will a full out brake job, new fluid booster fix that?

I heard the boosters on these vehicles are problematic, that would be my first guess.