I'v had my 93 ta for a little over a year now and as long as i remember my blinkers have been slow to turn on while the headlights were on. The right one was especially slow to turn on but they were both fine during the day when the headlights were off. my right blinker recently quit on me completely when the headlights are on but it still works fine during the day. I pulled all the bulbs front and back and switched them side to side and nothing changed. as soon as i turn the headlights on, my right blinker goes kaput.

 

You'll probably have better luck with this on "General F-Body Tech".... the blinkers don't interface with the PCM.