sounds like you have 2 problems.... the 1 bar in 5th is fuel cut. but at 0.5 bar you wont hit it it sounds like an ignition problem. most common problem at this time of year is wet plugs. if you still have the top mount intercooler, take it off, and then run the car on idle for 15 mins until its nice and hot. turn the car off, and pull the plug leads out. if you got steam, you have wet plugs and you need to dry them. if not. then you got me. 0.5 bar should be running sweet.