Issues in 406 coupe 2.0 operation

Hello there,
There are 99 406 coupe 2.0. I just bought it and started having problems. the atiker before me got lpg.

When the vehicle passes to LPG in cold weather, it stops at idle. Before going to the LPG, gasoline and speed, regardless of gear, is accumulating suddenly between 2500-3500 rpm and then gasped again. But if I change gear before coming to 2500 rpm, it doesn't make sudden heap and jump. then it works more stable than gasoline when it gets warmer after a while and passes to lpg. it does it only on gasoline. I am very happy when the engine warms up in lpg

When there is nothing going on for a few days, the engine malfunction, airbag and brake light are on, it turns off after 5-10 seconds. Then it flashes again sometime.

what could be the reason for them?

the ignition coil or injectors may have failed