TLS low oil pressure

[Robg]

I have a 91 TLS with the Bravo conversion done in 1997.  Recently seeing oil pressure that decreases at high power and increases at low power.  My mechanic called Lycoming, who recommended we check to ensure that the correct lower exhaust valve seat was installed.  1700TT with about 900 since the coversion.  Three cylinders pulled and reworked/overhauled since that time, one by a prior owner, two since I've owned it.  I've owned approx 3 years.

Apparently, the wrong part number is installed for the valve seat and the correct ones are $200 each.  Question to those knowledgeable about this marque:  Does the Bravo conversion come with all new cylinders, or is it a kit to modify existing ones?  I'm trying to figure out how the wrong part number would have been installed on cylinders that have never left the engine (assuming logs are accurate and I've had no occasion to think otherwise since I've owned it).  Second question, if the part number that's installed is for the -AF1A engine, would that cause the symptoms I'm seeing now?  (Oil pressure is confirmed accurate, since I the factory gauge plus OP on my JPI that uses a different transducer).

Appreciate any insight from those familiar with this engine.  Thanks, all.

[LT4BIRD]

Like how low? Below 50psi? The heads should have no effect on oil pressure even if the wrong seats were used.