Idling ok, it seems to starve fuel; then pops or just putters.

Peter, You still have a Justy on the road? Wow, good for you! They were definitely economy from the start. OK - so - I would suspect an air intake leak, engine vacuum leak, or lack of fuel pressure. Last, you could have an exhaust restriction, such as with the catalytic converter. Have a diagnosis performed to get a good answer. Good luck, -Dave