Help Low compression in all cylinders

Hi all

I have a 1991 V6 200hp TXRP engine. It has 1400 hours on it. I recently replaced the fuel pumps and spark plugs and thermostats. It ran perfectly for awhile then developed a tapping noise coming from the number 1 cylinder. So one day i decided to use Marvel Mystery oil to clean the the piston rings. This seemed to work and the tapping noise went away. Then a few days later it started to loose power and would not go past 3800 RPMS. So i checked the plugs and they were wet and fouled up. I then did a compression test and i had the number 1 cylinder had zero pressure. the remaing cylinders were all below spec and the #4 and #5 Cylinder had barely any pressure. And now it runs still but cant go past 3800 RPMS and now it seems to run hotter than usuall there are no alarms. So what i am wondering is should i replace the powerhead or would it be worth it to rebuild the powerhead. Any help or info would be appreciated. thanks

matt

[jb123]

plugs look NORMAL just wet ?

you could do a heavy shock treatment with ringfree or seafoam.

could be head gaskets most unlikely both sides.

lastly pull heads and have a look see.

i THINK if you scored a wall or 2 you would se it on the plugs......

you DID get the LP pump gaskets back in place correctly....didnt you ??