I have a yth2448 that runs on one cyl.(rs). ls has compression and spark & valves are set to 4 & 6. propane to left side does not improve it. ANY SOLUTIONS?

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My guess is you have a leaking valve. The compressed air in the leak down test is closing it. Remove the heads and lap the valves. Check the valve stems are true and not sticking. The variation is compression 50 v 30 is too great.

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There are at least three possible reasons for no psi in cyl No 4.
1. Burnt or damaged exhaust valve in that cylinder
FIX Remove head and replace faulty valve
2. Blown head gasket (water mixed with sump oil shows milky on dipstick and steam or water coming out of exhaust tailpipe, radiator water disappears )
FIX Remove head, grind flat and assemble with new gasket.
3. Broken piston rings, or cracked piston or burnt hole in piston.
FIX replace faulty parts.
Squirt some sump oil ( 2 or 3 spoonfuls ) through spark plug hole,
spin motor , and if compression PSI improves then it is rings or piston, if no PSI then it is faulty ex valve !!!

Code340 means the computer is not getting a signal from the cam sensor for one bank. Since you replaced the sensor, and given the fact one side has no compression, it could be that there is no signal because that cam is not turning.

You replace the spark plugs with the factory spec
plugs every 3 years

You replace both upstream O2 sensors every 100,000 miles

The COP ignition coils can last 2 years or 8, but they all fail by then

With no experience & me not writing a book here, on how to diagnose,just replace all the coils

Get them from Rock Auto

The codes you get are not much use as they are not accurate
The coils act up in different ways & set all sorts of codes

Take a compression check. If one cylinder is a lot lower (more than 10%) than the other chances are you either have a bad or leaking valve. Try to loosen the valve adjustment slightly in the low compression cylinder and sees if it improves. Maybe valves are just set too tight. If it is still low you can try squirting some oil in the spark plug hole and test again, if compression increases the rings could be loosing compression past them.

So your codes are: Multiple random plus misfires on 1,4,8. Misfire during startup, and ignition coil E (cyl 5) primary or secondary circuit malfunction.

You said that four new coils were installed. Perhaps the coil to spark plug order and the firing order have been scrambled. The spark plug wires may be old and leaky--especially if they are the originals from 2003. You could have a vacuum leak into the intake manifold, the EGR valve could be sticking open when it should be closed, the fuel filter could be clogged, the fuel pump pressure could be too low or stuck at the idle setting, the fuel injectors could be dirty, and cylinder compression could be low (putting on the wrong size o-rings when reinstalling injectors will prevent proper compression.)

P0304....Cylinder 4 Misfire Detected
could be a burnt out valve??

SOUNDS LIKE NO FUEL TO 2,3,5,8 CYLINDERS

It might have a damaged valves caused by slipped timing belt making the piston and valves banged each other. That is why the compressions are low. Big job.

how many cylinders 4 cyl 1342 or 1243 6 cyl 134652 hope this helps