overheating

my 95 chevy cavalier overheats when i put on the blower motor for the heater. what can cause this.?i also got a code for egr several times .replaced it and still same code.:disappoin

1) Did you use a gasket for the EGR valve?
2) Was it over heating befor you replaced the EGR valve?

It sounds like an open port, or window to the Intake giving a lean condition to cause over Heating.

thanks for the help dan , but yes it calls for 2 egr gaskets, and it was overheating before installing the new egr replaced the (2)o2 sensors,map,tps,egr and the car still surges and sometimes shuts off at a light, its possible but are u talking about the port (head)gasket? and if it is the intake(leaking) wouldnt it idle high or no.?

Consider doing a smoke test for unmetered vacuum leaks.
Focus on EGR, PCV, and Intake System.
See http://www.automotiveforums.com/vbulletin/showthread.php?t=1058320