yeah it was a big back fire with lots of flames. lol

I think something has got wet. Once the engine has covered a few miles its fine. Yet left parked in the rain again for a few hours, fired it up to go home and it did it again after a few miles of driving, then after a few more it ran fine. So once the engine has warmed up its obvisouly dried up the problem.

Must have a bit of moisture getting in somewhere from the rain.