Not starting correctly

I have a 97 sts and it is not starting correctly. Basically when the car is cold it starts great 1 turn and vroom. but once it gets warm it is harder to start. it takes like twenty cranks to start then it fires ups drops dow to 200 rpm and back up too regular operating rpm..could this be because of the antifreeze i am using or a cts sensor that is about to go bad. the fuel pressure is fine any thoghts please i need some mechanical assistance. http://www.lincolnvscadillac.com/images/smilies/mad.gif http://www.lincolnvscadillac.com/images/smilies/confused.gif http://www.lincolnvscadillac.com/images/smilies/eek.gif:screwy: