The Nissan Path

My 91 pathfinder is running very rough, driveable but rough. Has low idle, even with adjusting. Far as I can tell there are no loose or missing vacuum hoses. Has new plugs, wires, cap, rotor, air filter, oil change and filter, and new fuel filter. Sometimes it stalls even after being warmed or driven for a distant of say 30 miles. In actuality when it stalls it is pretty much when it feels like it, but it is at a full stop. The idle is really inconsistent, sometimes it idles at 700 rpms and then drops to 200 rpms and either tries to stall or bounces back. Also there is an exhaust manifold leak, I didn't really think that could cause a rough idle, but at this point I will try anything. If anyone has had this problem or knows where to look or what to replace please chime in, this is the family car right now so it kind of needs to be dependable.

Vacume lines can look good but can still have leaks, the original lines may be getting hard and wont seal correctly

Mass Air Flow sensor needs cleaned ?

Cat is getting clogged/02 sensor ?

Gas cap not sealing correctly ?

Maybe some obscure sensor thats really hard to get to and cost alot ?

Couple of shoots from the hip