2002 Ford Ranger 3.0 intermittant misfire

Failed CA smog P0305 Misfire detected.
My son who drives this truck 95% of the time informs me that when stopped at a light the truck engine started shaking quite a lot (must have for him to notice) and it stopped when he drove away. He says this has happened to him twice in the last month,
Removed plug 5 it looked fine nice light brown colour.
Dropped it and broke the insulator.
The plugs have not been changed in approx 90000 miles so new set of plugs fitted.
All the plugs had the same light brown colour.
Plug lead rubbers cracked when removing some of the so new set plug leads fitted.
Tried shorting out plugs at coil pack, slightly detectable change when 4 and 5 shorted
The other cylinders have a more pronounced change when shorted.
Good strong spark on all cylinders.
Engine runs on tick over with a slight miss now and again.
When driving no detectable miss can only detect it at a stop but not all the time.
Squeak coming from camshaft sensor, new sensor fitted. The pickup on the old sensor looked perfect no play in the shaft but squeaked and did not feel right
Connected vacuum gauge runs at 14” needle steady as a rock, blip throttle vacuum
falls and the rises to about 20” before returning to 14”.
Did a compression test 1 2 & 3 160 150 165
4 5 & 6 125 125 140
Connected laptop to truck running” Forscan” and when driving it the misfire counter only counts up when stopped and at tick over.
I don’t know how to put the graphs etc of “ Forscan “ into this document but
Bank 1 runs at a long term fuel trim of +8 bank 2 runs around -8 the short trims change and average around 0.
I thought this might be due to a faulty O2 sensor on bank 2 new one fitted no change.
I have OBDCOM and could download these readings truck warmed up on tickover
Then raised to about 2500rpm.
I have only in the last couple of days started to learn about fuel trims and am somewhat perplexed by the differences in LTFT on the banks.

In checking I found the expansion tank empty and the radiator needed a quart of antifreeze. I changed the oil no sign of water contamination. I change the oil every 5 to 6 t housand miles uses maybe a quart in that period.
I changed a few vacuum lines because of ozone damage but no cracks etc found.
The fuel injectors cylinders 1 2 3 and 4 sound the same with a stethoscope can't get to 5 & 6 because of intake plenum.
Everything i have changed to date I have done for a good reason (to me at least).
I don't believe in the shotgun approach to troubleshooting so some guidance would be appreciated.
Coil pack ?
Injectors?
Because of the low compressions on Bank 2 I am beginning to suspect a head gasket starting to fail ( the truck has never had any overheating problems) or maybe exhaust valve recession. The heads on these Ford Vulcan engines are prone to it apparently.
My TR6 is a lot easier to work on strombergs and all.
Well folks a long tale of woe but I believe the more information you have on a problem helps.

Ok well your compression on 4 and 5 is well under spec and is surely the cause of your misfire at idle (which is a good indication that its a compression problem ) at higher rpms there's more pressure and less time for whatever is leaking to leak. Anyways the next step is to perform a compression leak down test with plug 4 5 and 6 removed (to check for compression leak between cylinders) if you need further instructions on how to perform this we can guide you further.

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Thank you for your quick response
I will get a leakdown tester .
It will be a few days before I am able to work on the truck again I will keep you posted thank you

Update on ford ranger missfire
Upon inspection using a magnifier i found tracking marks on the coil pack end near the primary plug.
Coil pack replaced missfire reduced but still detectable intermittantly at tickover.
Did a leak down test cylinder 5 @ 70 %
Decided to remove the head. Cylinder 4 and 5 exhaust valves had recessed 1mm into the head and showed signs of pitting.
Cylinder 6 receded about ,7mm.
Removed the other head Cylinder 2 had receded .7mm All readings taken in comparison with cylinder 3 the one with the best compression.
Heads taken to a shop to have new valves and seats. The "good" head cylinders 1,2 &3 was found to have a crack on #3 exhaust valve it had not yet reached the water passage.
Now the engine is fine.
Point of interest Where before bank 1 was running at a LTFT of +8 and bank 2 at -8 STFT averaging 0
they both read positive now at 5.4 STFT averaging 0
Would I be correct in assuming that the ECU was subtracting fuel because of the missfire on bank 2 and increasing it a little on bank 1 to keep the RPM at idle ?
Thank you for your assistance I think i knew the heads had to come off but didn't want to accept the fact.
Smog passed and truck sold.