Troubleshooting my rough running 93 Loyale

[DaveT]

This car is in a garage, driven a couple times per week.

Suddenly, yesterday while driving, - Runs rough.  Idle, dies.  Idle in N dies.
I did manage to drive it home, Seemed to run ok down the road, not acting like starved for fuel.
In N, press the gas and hold, the RPM goes up, [example 2500].  
Then after a second or 2 drops about 500, and the roughness returns. 
Does this regardless of what RPM you get initially - goes up, then drops back.
Does this hot or cold.

Capped the vacuum tap on the passenger side, no effect.  This eliminates EGR, Evap, HVAC controls as possible culprits.
Capped the vacuum tap for the brake booster, no effect.
Distributor cap & rotor look normal, not loose.
Timing belts are good, not jumped.
Swapped the MAF, no effect.
Swapped the IAC valve, no effect.
CTS has nominal normal readings.
Fuel pressure normal 22-23 PSI.
Ignition coil & igniter swapped, no effect.

ECU swapped - Still runs crap / same, but doesn't quite die at idle in N

Running out of ideas....

[bushytails]

I haven't troubleshooted that problem on one of those, so just some random ideas...

Does fuel pressure go up to 35+ when you give it gas, and stay there as the rpm drops?

Did you recently get gas, or other chance of contaminated fuel?  Sample a bit into a clear container from the pressure test port if not sure.

Does the exhaust coming out the rear feel normal, with distinct pulses per cylinder as it idles?

Does it feel like all cylinders are weak, or like one or two cylinders are cutting out?

Coolant level and condition normal?

 

[DaveT]

Coolant normal.  Fuel pressure stays steady at 22 PSI, just like my other EA82 SPFI wagon.  Never moves vs throttle position or load.

No recent fuel up.  The roughness seems more random than cylinder specific. I'll try to check the exhaust pulses tomorrow.

I also swapped the distributor since the original post, no change.

[bushytails]

I'm thinking of the mpfi version.  they were still doing spfi in 93?  Shows how many of those I've worked on.  lol  Sorry, my bad.

egr valve stuck open?

 

[DaveT]

SPFI in 93, I think I read to 94.

I checked the EGR valve after the OP, and yes, it is working normally.  Took it off to check that it wasn't stuck open, etc.

 

[SuspiciousPizza]

Have you checked the values and calibration of the TPS?

I'm not as familiar with the autos as I am with the manuals. Isn't there a drop down circuit that senses when you go in gear and it'll drop the idle?