'94 LT1 runs rough when hot

My '94 LT1 runs smooth for the first 50 miles until engine temp gets hot. When it is hot and I am in stop and go traffic with the A/C on, engine surges and sometimes runs rough. At that point, engine
hesitates, surges and pings when accelerating. Any ideas what is causing this? No codes showing up. Is it the optispark? Would really appreciate any ideas to correct the problem because I love my 'vette. I is my second in 11 years of vette ownership. Thanks!
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
BigAl wrote:

On the L98 I had the EGR stick and mess up idle with no code. Also caused a nasty 'hiccup' on throttle closure at 35-40 mph. Yes, definitely worse with the A/C on and with coolant above 160 deg. Not noticeable when engine cold and ECM working in open loop (O2 sensor not in the loop.) No ping on accel though.
I put off pulling the plenum to get at the EGR for several weeks.
What really got my attention was the sudden red face I got when the engine died as I started a left turn -- then the green arrow went out and the opposing traffic ..... -- the guy in the Mustang waved nicely then threw a bird at the freshly detailed but stationary 'vette ... as he maneuvered around me. <<:-O
HTH ...PJ -- PJ '89 Hookercar '02 e-blu coupe
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.