CrazyMacaw

Greetings,
I have a 97 GC Laredo 4.0L 120K miles with what I think is the elusive power loss/ stall issue. Originally I diagnosed it as the ECM because I could push on the case of he ECM and get the engine to stumble and die. I replaced the ECM and it ran great for about 2 weeks then started having issues again. Same deal, I could press on the casing and get it to stumble and stall so I got a second ECM and things were great for a week and now the problem is starting again, but this time I don't think it's the ECM because I can press on the case and wiggle the connectors and it doesn't cause any issues like the last two did. It's got fresh plugs, wires, dist cap and rotor. It usually doesn't set a code if it just stumbles but if it totally stalls it will sometimes set a code 43 which I think is a general misfire code.

I've noticed a few things that I'm hoping might be pointing me in the right direction and I'm hoping someone out there might have some insight and advice.

The problem occurs at driving speeds as well as when at an idle, both hot and cold, it's even happened when using the cruise control and when the power came back the CC was still engaged and it brought the vehicle back to speed.
When the power dies, the motor itself is still spinning at a pretty high RPM, I can tell because if I mash the accelerator I can hear my intake make that nice K&N open air filter buaaaaaaah sound, and also the transmission will downshift to second gear and the vehicle will start to slow down even faster (like an engine brake), also I still have good oil pressure, and my alternator is still putting out electricity according to the instrument cluster. However even though the motor is spinning at probably 2000-2500RMP the tach drops to 0.
What I'm not sure of is how the tach gets it's signal, and what sensor it's reading is based on. I'm guessing the tach gets its signal from the ECM unlike the old days when a tach took it's signal from the coil directly.
Based on this I'm going on the premise that its not a fuel problem but an electrical problem since no fuel wouldn't make the tach drop with the engine still spinning if whatever tells the ECM to send a specific signal to the tach would still be getting signal from the spinning motor.

I've checked the ASD relay which as I understand controls the coil, injectors, and fuel pump relay and will shut them down if no pulse signal is present form the crank sensor. My thought is that what ever sends a pulse to the ECM like maybe the crank or cam sensor is failing or there is maybe a wiring issue and that in turn is causing the ASD relay to shut down which kills the fuel and spark.
Since the crank and cam sensors are simple hall effect switches and have no high or low range I wouldn't expect either to set a code if they failed or if their wire was faulty?

I'm thinking of jumping the ASD relay temporarily so it can't disengage to see if this eliminates the problem. My thought is that if the relay can't open the fuel and spark will continue to function and if the issue was a wire between the ECM and ASD relay things would run good since the relay stays closed but if the issue was a sensor the thing would start to buck and jerk and maybe backfire since it would probably be firing out of time if it didn’t just stall out.

What's your thoughts?