I have an 86 k5 350 auto. No lift.... While driving the infamos Mex 1 ( a 2 lane nightmare) down to Cabo, we encountered less than accepable handling..ie. swaying, drifing at higher speeds 50 -70 mph. On trails or the beaches it wasn't too noticeable Our bf goodrich a/t's are new and inflated to 34 psi (on the highway of course). The back of the truck was pretty weighted down with gear, and a rear tire/ gerry can rack which is also new to the truck seemed to not help the situation. Could this be the culprit?? Any solutions?? ADD A LEAF? ADJUSTABLE AIR SPRINGS?