Q: The car sometimes run well but sometimes stalls - is this an exhaust problem?

If it involves your daughter you’ll want to be mindful that "stalling" anytime and anywhere, except in your driveway, is extremely dangerous because it creates a crash senario. If a vehicle "stalls" in an intersection, which is not typically expected to be encountered by other motorists, other cars may simply crash into you. Consequently, the acceptable amount of "stalling" for a vehicle driven on roads and highways is considered to be zero.

I would first have the stalling issue diagnosed and only after that is fully resolved, consider the exhaust repair (of course, that doesn’t mean the exhaust system is unimportant - leaking exhaust is a hazard, too - it just simply means that you have to have a reliably operating vehicle before you consider putting money into the exhaust). As far as the catalytic converter is concerned, if the converter has rusted away and/or the flanges are leaking, yes it should be replaced as a matter of course but if the converter is intact, some tests have to be done to determine if it has really failed internally. Please let us know if and when we can help you resolve the engine stalling issue.