Hey Patrolman and crusty - sorry, just found my old password and was able to log in again after ages.
Patrolman - sounds like you have an air leak into the manifold or hoses that feed it. The oxygen sensor will regulate the fuel input to match the airflow, so will idle fast.
Crusty - looks like a vacuum solenoid to control any vacuum operated valve/servo. The TB42E runs like crap when cold on petrol. LPG is sweet and smooth no matter what the temp.

All my mods have been running sweet, inlet air, cooling, vacuum and clutch.

Did the wiring reduction to the clump of terminals and spaghetti near the battery feeding the engine. Added a fuse block and lost about 1/3 of the wiring. The original looked like a dozen seperate designs were used on the wiring and none of them agreed with the other. I've seen better jobs on farm utes with 240v house cables.
It's now slim, efficient and logical. Organised and labeled the mess of relays as well, and added an upgraded headlight harness, protected rear cargo power supply, reverse light override, relay fed driving lights and interlinked switch controls.