87 xj 4.0

This is what AI said.
Too Low is Bad: Very low resistance (like <2K Ohms/foot for a stock-type wire) can cause weak spark and misfires.

my plug wires actual resistance values.. used digital multi.

Cable to coil.562ohns
1 ) 790ohms
2 ) 748 ohm
3 ) 508
4 ) 966
5 ) 1064
6 ) 614

Whats the fsm value?

 

Here's the thing... Your Jeep OHM readings are what I would consider normal...Most "stock" replacement wires run in the range you have {350ohms/foot}...Super high or low would be a problem as well as one wire in the set way off from the others...High being ready to give up conductivity and low being probably water soaked etc...And that's the reason why AI is giving the answers you're getting..
High performance is another story : I've got plug wires that run 50 OHMs per foot and if the plug wire is left off the plug the sparks will jump 3 inches to ground !It looks like a lightening bolt...lol...

 

There is no fsm value?
100ohms is low?

 

FSM state that the ignition cables are supposed to be 3,000 Ohms/Foot Minimum and 12,000 Ohms/Foot Maximum but take that for what it's worth it's a huge swing and too high across the board IMO....
EDIT: I've got Taylor Thundervolt 8.2 wires and they're actually 40 ohms per foot... Low ohm wires won't hurt the 4.0 as long as there's no RF/static coming off them to mess with the electronics...Exhuast pipe is nice and grey....

 

From my '88 FSM. This assumes OEM wires and plugs.

IGNITION COIL WIRE
Remove ignition coil wire from coil and distributor cap.
Check terminals for corrosion and clean (if necessary). Check coil
wire resistance. Replace wire if resistance is excessive.
HIGH TENSION WIRE RESISTANCE (OHMS) TABLE
---------------------------------------------------------------------------------------
Wire Length Minimum Maximum
0-15" .................. 3000 ................... 10,000
15-25" ................. 4000 ................... 15,000
25-35" ................. 6000 ................... 20,000
Over 35" ............... 8000 ................... 25,000

 

So making the calculation with the wire lenght 550 is the right measure . Plus minus 50ohms .seems 4 and 5 cylinder is reaching the 1k..

 

OP
keep in mind that the shop manual (in a different, earlier thread you said you had one) is setting specs for plug wires that will not only allow the engine to run properly but will allow you and people in vehicles nearby to listen to the radio. The radio...static/ interference problem is the reason for "resistance" plugs and wires.
As noted by others above aftermarket solid conductor wires have very low resistance and do not cause " misfire" etc