It feels like someone is flicking the engine kill

[Boris]

It maybe your Throttle position sensor breaking down. This usually happens when you either slow right down or come to a stop and the engine dies on you. Which if it does and catches you out, you can end up on the floor :'(. Unfortunately unlike the TPS on a FZS 600 which is easy to get at and replace. Those on an FZ6 require the tank, airbox and injector bodies removed to access the little blighter. Which then has to be set up with a voltmeter. Price for a new one is around the £90.00 mark. Don't buy second hand, it ain't worth it.

Hope this helps.