Like I said, misfires can be many things. It's tough to diagnose over the web. I'm a hands on type, run it type. I just started with the two most basic fixes, O2's and vacuum leaks and it never ends with that but it might/might not show improvement. Couple of other simple/common things to check are the PCV on passenger side valve cover and of course the Idle Air Control solenoid which if you don't know the condition of it's bore and tip then you should familiarize yourself with those. Once checked and cleaned if need be and the motor is in top shape it won't carbon up again for a long while. Mine has remained perfect for nearly three years, bore face still shines.

Largest factor in carbon accumulation is the A/F mapping of the ECM prom. 96's being the first GEMS Disco's seem to have had teeth cutting issues that where later addressed by remapping the A/F trim levels (updated proms through dealers) and mechanical improvements to include factory installed carbon cutting exhaust valves.

I always start with the simple (since I cannot see or hear it) and work down to the more complex if I offer an opinion/suggestion. Stuck exhaust valves being down the list. Sometimes erratic misfires in the later 97-99 1/2 trucks can be due to corroded ECM circuits. Who knows eh........ Do drive the truck more often, the miles on the odometer will not matter as these are getting cheaper by the day to buy.

VSS seem to make the speedo needle bounce when acting up, notice that? VSS is usually chaffed wires, not the sensor but not to rule it out either......

 

I believe he is on the correct pathway to improved running. I wish I knew more about what he said.

I have a "early" 97 (mfg in mid 96) (GEMS & Pre-AEL). I had a variety of codes associated with misfires, went thru a lot of carboned up plugs, poor milage, random stumbles and worked my way thru a variety of issues.

First get an UltraGuage and see what the numbers tell you. Learn more about what they should be as well. Run the best gas you can, 93 octane is what I prefer either Shell or Exxon or major brands, no 87 or 89 octane.

Put in new Chmpion Coppers or other simil;ar cheap but good plugs and a good set of plug wires.

Get CRC or similar brand MAF Cleaner, IACV Cleaner, and Techtron additive. Thoroughly clean MAF and sit it aside to dry.

Remove IACV from Plenum and concentrate on cleaning the orifice it fits in. Be careful with the IACV itself, just spray it off and do not try to twist it. Gun cleaning kit is ideal. Do the same for the PCV ports. Clean the inside of the plenum around the butterfly valve. Some people even remove it for cleaning, I did not.

The two little vacumn hoses that connect from the valve covers to the intake are often are a source of problems, replace them with the correct new hoses. They are different diameterts on each end, so buy the correct ones (AB has them at a fair price).

The above may not fix everything but it sure will make a major improvement in how it runs and is not very costly. Then if problem persist you have ruled out a lot of possible contributors and not thrown away any money doing so.

The fact that it is all on same bank, could indicate VSS or ECM since a VSS that thinks you are exceeding 118mph will shut down one bank then the other.

And see what the O2 sensors give for live data, that will tell you if they are working correctly or not. Good Luck.