Look for tears in the tie rod end boots, leaking/oozing 'fluid' from the ball joint, and any other irregularities.
How low are you? Maybe you're hitting your bump stops? (I doubt it, though) ... maybe you should just hold the steering wheel tighter. <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/smile.gif" border="0" valign="absmiddle" alt='
'> I can't think what else it could be...
Maybe imbalanced tires? Or even alignment? Did you get an alignment since you put in any of the suspension bits? (bushings, shocks/springs)