Hi, can anyone help me with this problem? I own a Vauxhall Zafira GSI with a Regal Stage 3 conversion, which has been on the car approximately 8/9 months. All was fine and I took it to Regal for a rolling road power run and had new iridium plugs and air flow meter fitted. Three to four days later, I noticed the car was running lumpy on idle and when driving, you could hear a really loud waste gate noise. I took it to Regal and they did a Tech 2 test and said all was ok but that cylinder number 3 was breathing heavy due to the piston crown being burnt off and the compression ring/oil ring. So, I took it to Vauxhall and they said there was no sign of the crown being burnt off as far as they could see when removing the spark plugs and said that if it was piston or compression then you would feel a misfire all the way through the rev change - and you donít. So, I then fitted a new boost control valve and itís still lumpy on idle. Please can anyone give me any advice as I am at a loss. The experts are giving me conflicting advice and I donít know what else to do. Any ideas would be greatly appreciated!