[amorlv70]

Hello.
Over the last 3 months my car developed a slight misfire at cold on cylinder 5, which quickly cleared up after 30 seconds or so.
It is on 146,000 miles, LPG fitted at 115k.
I replaced the spark plugs, then the coil of cyl 5 and it made no difference, so I stopped using the car as the misfire was getting very bad.
Fastforward a few weeks and I have done a compression test, it has failed quite dramatically:

Cyl 1: 165psi
Cyl 2: 65psi
Cyl 3: 90psi
Cyl 4: 65psi
Cyl 5: 30psi

To me this is obviously not right, and I can probably rule out plugs and coils.
I have no symtoms of HG failure coolant is still green and oil normal colour. So is it possible that my head has suffered with valve recession?

I was under the impression that these cars don't need flashlube as they have hardened valve seats. My fitter didn't install flashlube so I assumed it wasn't necessary.

Before I take my engine apart, does this sound like a valve problem? Should I try and source a new engine/head?

This car is very sentimental, and has been looked after meticulously, so I will give it whatever it needs.
Thanks

Edit: Is there anything else that could be the problem? Piston rings? Spark plugs on the problem cylinders are pretty fouled