I had a new exhaust fitted around 6 months ago because the back box burnt a hole through the top and the middle section wasnt very secure.
When I switch off the engine, it sounds as though its blowing air out the exhaust.

I'm a little weiry about starting the car with only 3 leads connected, its not going to damage the engine is it? What happened when I find the misfiring cylinder(s)?

THanks.

Jason