i have always had trouble getting heat out of my 94 2.2L. it heats a little bit, but not much. when its 30* outside, it works fine, but when its 0, its a little chilly in the car. have replaced everything related to the heater and cooling system since i have owned the car. radiator, thermostat, heater core. the only thing i can think of is the vacuum lines that actuate the flappers in the heating system.

one observation i have made is that when i go up a steep hill on the highway, and i am giving 75+ throttle percentage, the air will turn cold and start coming out of the "vent" locations in the dash rather than the defrost location.