[cadillac531]

Hi gang. I'm having an idle quality issue in my 91 and would like to get some feedback from you all.

Idle quality was pretty bad a few months ago. Injectors were original and leaking down, the wires and plugs were all original as well, so I changed them all out. I threw in a new set of injectors, plugs and wires I got from Jerry, gapping the plugs to .035. I also found the pumps weren't holding pressure key on engine off and replaced those as well, and for good measure changed out the fuel filter. The pumps were only 6 years old.

After all that, the car has improved low end drivability, and pulls very hard. However, the idle is not very smooth and I can't seem to pinpoint what the issue is. Currently, with key on engine off, and FP2 fuse pulled, I get 50 psi of fuel pressure (I do have to cycle the ignition a couple times to get there.) With FP2 fuse back in, it shoots to 50 psi. When the pump stops, the pressure holds around 42. It then leaks down very slowly, perhaps 1/2 psi every 20-30 seconds. At idle, fuel pressure bounces back and forth between 41 and 42. There are no check engine lights and it is very smooth everywhere but idle. I put a new IAC in it just to check and that didn't make a difference. I also have a 1 Bar MAP on the shelf from another project, and swapped that out with the one in the car and that made no difference either. I checked the plugs and they are good, with no soot or oil on the strap or electrodes and color is pretty good.

I ohm checked the coils through the wires and got the following values:
5,8: 6.96K
1,6: 7.09K
7,4: 6.90K
3,2: 7.13K

According to the FSM, these ohm readings should be fine.

Any thoughts on why I can't seem to get a smooth idle? Many thanks in advance.