Fabia MK2 1.2 6V CHFA red manifold

Sorry for bringing up this topic but i have a really bad problem. CHFA engine heat the catalytic converter from the manifold to the flexible part of the exhaust like hell. Runs on idle at 600C degrees and in roll above 800C degrees at 2000-2500rpm.

The engine works and sound great. Managed to do some work, rebuild cylinder head, new head gasket, new valves, new timing chain, new coils and spark, new Lambda sensors, changed the catalytic converter and still does the same. i really don’t know what to do. car runs on aftermaket landi renzo LPG and petrol. both fuels heat up the catalytic converter. exhaust is not blocked. 

I really left up of ideas, don’t know what to do next.