3ms is a little higher than I'd expect in double fire mode (normal injection mode). In that mode I'd expect 1.9-2.5 with almost any system that has properly sized injectors for the HP (N/A of course). If it's reporting total PW for 1 intake stroke then it seems OK.

Is the MAP sensor mounted directly to the manifold on a Miniram? or does it have a vacuum line to it? I've seen vacuum line get damaged from having a low point in it, which collects fuel and slowly rots it (not the best quality line I suppose). This rotten line can get soft and collapse a little under vacuum, or crack a little. But, you've covered the lines already, so I won't put any money on that being the problem.

But still, idle misfire problems are typically vacuum leaks, plug wires, bad injectors, tricked or aged O2 sensors, and clapped out distributors. A V8 can hide a misfire under load quite well. Oh, and misadjusted valves will do it too (like if you tighten until you can't turn the pushrod, and then give it a half turn instead of tighten until you feel no slack, hehe)

Is the idle misfire there when the engine is cold? What about if you are in neutral and hold the revs just a little higher than idle?

 

just a thought, do you have a compression gage that holds pressure after you have spun the motor over? if so, does it have a release valve on it so you can release the pressure without unhooking or removing it? if it does, try this. unplug the IAC & the timing connector. then pull a plug on a known good cylinder & start the motor & with it at a stable idle speed, release the pressure then watch how fast the gage climbs to maximum pressure & make a note of the max pressure & how long it took to get there. do the same on the bad cylinder. you may want to check more than 1 good cylinder. also, be sure to ground the loose plug wire before you crank the engine up.
i didn't notice if you said it has the miss hot or cold, but you want to do this during the time it is missing the worst.

 

The reson I asked if the miss only happend when hot is that I have a freind with a 90 Sub that had the same type of miss, and he had changed everything twice including the ign module. As it warmed up the miss would get worse and it would get a little lean 132blm, I found when I disconected the timing conector and watch the timing with a light as it warmed up it gained 34 deg at a idle. I replaced the module with a used one I had and problem went away. He had replaced it with a oem unit from the dealer. In the shop I used to work at we would have to some time change 2 or 3 before we would get one to work rite. Just somethig to try.

 

Yes, the miss is there hot or cold. It's rougher in general when it's cold, but the miss is pretty much the same.

 

well, hopefully none of these ideas has been tried before, i'm trying to think unconventionally.

1) rig up a grounded 9th spark plug somewhere you can see the gap. hook #2 wire to this plug and run engine, observe spark quality. try the test plug on another cylinder or two for comparison sake.

2) try different gaps/plug indexing in #2. try a 0.025" gap or a 0.060" gap and see if it responds any differently.

3) hold the engine at 4000rpm for a minute or two, then shut off. does the #2 tube come around to the same temp as the rest? or is it still cold? this should rule out bizarre idle airflow distribution problems with the intake.

4) verify #2 is timed correctly (you'll need a well marked harmonic balancer, or at least a line scribed 90* before the 0 line), use timing light on #2 and verify it's firing in correct time (90* before #1)

5) if you have any way to beg/borrow/steal different sized injectors than what you are running, swap them into #2 and see what happens. If you are running 24# injectors, try a 28 or 22 or 19 in the #2 hole just to see if it responds. this will help determine if it's simply an air-fuel ratio problem in that hole. If it does respond (for example let's say that cylinder runs better with a 19# in it), then you know that hole is starving for air.

6) try swapping #2 and #4 injector plugs (that is to say, power #2 with #4's connector and vice versa.)

is there any casting flaws/molding issues with the miniram intake that might be causing unequal airflow to #2? some kind of obstruction ahead of the #2 runner? cracked runner?

any chance that the rocker stud on #2 intake is leaking air into the runner? (if i remember correctly, the AFR heads like my fastburns on my 71, the rocker stud protrudes into the runner).

any chance of bolting on a stock TPI intake (or a stealth ram or something) just to see what it does? i know none of us have stealth rams just laying around but maybe a stock tpi at least.

plugged /crushed header tube on #2 and it just can't breathe? (maybe under the car near the collector, hit something?)

you might consider welding a bung into the #2 header tube to analyze just that one cylinder as well (or better yet, all the tubes, so you can check them and compare at will).

since the combo worked, then stopped, i'm inclined to go with a parts failure - crushed header tube, cracked intake runner, leaking rocker stud which protrudes into intake runner, something along those lines.