95 TA LT1 Help plz }{ running odd

[muddeamon6]

I have a 95 TA Lt1 it runs fine but after 35 -45 min of driving on hwy when i start to slow down on city streets it acts like it wants to choke out and hesitates real bad motors not running hot maybe 190 to 210 tried premium and unleaded fuel replaced tho o2 sensors and cat and optispark new motor and trans water pump in short replaced almost every thing. so any ideas on what it might be im completely lost

Thanks for the help
Dave