So i have this problem that is keeping me from driving my 1990 460. I changed the IAC because it was idleing at 1100 rpms. Here is a video of the problem. I had posted it to a group on facebook and they said it could be the TPS or outher stuff. My dad said it could be plugs and wires need to be replaced because he said it sounds like it's missing. The truck will try to stall well it's going down the road. It's been more than 60,000 miles sence it had plugs and wires changed.

 

I must ask, did you pull codes? Just because the light isnt on doesnt mean there are no codes stored in continuous memory.

It does sound TPS related though.