I am about to buy a 1988 RX-7 but the owner says he thinks the engine is running rich, says he took it to a shop and they told him it was vacuum leaks and maybe a bad mass air flow sensor. Since I've never owned a rotary engine I don't really know what red flags to look out for and I'd like some advice. Finding the leaks could mean a lot of time but I'm more worried about it being something else that will be more mechanical that could be going on.
What are some definite red flags I should listen for, look out for?

Cheers