Am posting this on behalf of my mate who has a sri-t. He.s just fitted a k&n 57i cone filter and we've gone out for a test drive. The car drove fine until booting it slightly when it cut out. Pulled over and started it up again - its idling fine but when he rev'd it and let it drop, it cut out after going under 500 rpm. Tried again and same thing. He has recently (only couple of weeks ago) put a new vxr turbo on it himself and has had it serviced and mot'd since. It is running stage 3 but at the service only had standard cheap plugs put in. Could this have something to do with it? Any ideas appreciated!