V6 engine spazzes out on both LPG and petrol (intermittently)

The last few days I have experienced a loss of power on LPG. When this happened, I hear buzzing from the LPG controller.
It sounds like a relay switching on and off rapidly. So obviously I switch to petrol. But when I do, it idles about 1500 RPM,
until the aircon compressor engages, then it nearly stalls. It then seems the compressor cuts out, and engine revs up to
1500 RPM again. Also seems to lack power with petrol: can barely reach 90 km/h with pedal flat to the floor.
Still sounds smooth though, not like any cylinder is misfiring.
Next morning, it starts okay, and has full power, but after an hour or so, starts playing silly buggers again. So something is
screwing both petrol and LPG. I checked the PCM error codes - nothing but 12. I had a good look around, air intake is
okay, and can't see loose wiring or vacuum hoses.
Any suggestions?

 

You could be on the right track. Since yesterday, it won't run at all on LPG. I unplugged the LPG contoller
and it has since been okay on petrol. This unit (AEB) uses only TPS, exhaust oxygen sensor and
ignition pulse (RPM) as inputs (plus a few on/off signals like aircon compressor). I think the AEB black
box has died, and also corrupted either the TPS or exhaust signals, so the PCM is befuddled.