That's normal when you disconnect the (Black/Tan) EST bypass wire. I wouldn't think a little dent in the Y pipe would cause issues with the EGR valve besides, it's downstream from the O2 sensor.
Quick follow up --I haven't been able to work on the truck much due to the weather and not having time but I did set the timing back to zero with the bypass disconnected and then reconnected it. CEL lights are all clear again.
On my 94 --the O2 sensor is on the Y pipe just before the CAT --not on the exhaust manifold. So the dent is actually upstream to the O2 sensor in this case and on the drivers side of the exhaust flow (of the Y pipe).
I'll try to post up a picture of my dented y pipe since the weather is looking good and I have the day off..
Quick ALDL cable and TunerPro question on the INT/BLM (short term and long term fuel trims). What should I be looking for --they look to be 124-133 range..?
Also, the O2 sensor changes from 920 when cold and 60 when hot (I don't really know what these mean and what they should be..