Controling buffer: php/smarty or apache?

Hi, I am facing a strange problem. My site, even tough designed to appear quickly at user's browser, appears at "once". If I test the static HTML version it starts to appear as downloaded If I test the php generated version the page seems render as a whole. I am using smarty as a template and it seems to be related to a buffer somewhere: php/smarty or apache. I've used microtime and from the begin of the php script until after the smarty->display it takes from 0.05s (min) to 0.32s (max) Any tips of how can I figure out what is "slowing" down my site? tks