Been round the full engine bay checking making sure all connention plugs are on well. Cheked the ignition leads, they fine too. Spark plugs have a really big gap which will be attended to shortly when I can get a lend of some feela blades. The car idles fine on tickover (most of the time) miss fires at really low revs and light throttle but runs fine when its under heavy throttle and boost.

Wondering if it may be plug gap, but surely that would be the opposite? Run ok at low revs but miss under boost?

Starting to do my head in now.