Engine problems -Temperature related

I have a 1990 C4 L98 with some engine issues. Any suggestions would be welcome. The problems seem to be temperature related. When the engine is cold, or the air temperature relatively cool, say below 75
degrees, the engine generally runs fine. On hotter days, or after the engine has run for a while to get nice and hot, the engine loses power and runs very rough. At idle, the engine RPM oscillates up and down by a few hundred RPM when hot. Also, if I let the engine idle in my driveway for 15 minutes or so, it starts to over heat. That could just be a thermostat.
I recently replaced the EGR valve, and I still sometimes get a code 32 after a half hour of highway driving. The old EGR valve was clearly stuck open. Is there a sensor, like a temp sensor or O2 sensor that I should be looking for? Any ideas?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

It's a bottom feeder and tends to vacuum up all sorts of trash, clean it out of the front of the radiator.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.