I have a 1992 crown victoria. it idles and runs fine when cold or normal weather outside, but when it gets hot outside(80f-95f)it starts to sputter, the idle is very rough and i mostly hear it coming out of the exhaust pipes. (even with new plugs, wires and air-filter) oh and it has 2-1/2 exhaust piping after the exhaust manifolds (duals - no x or y pipe) and only has two catalytic converters

Your car may need a new dis. Mogul, or coil you can test the coil and the Mogul seems to be part of a healthy tune up , it seems to be the number one cause of ruff running and eventually no start. depending on the miles and maintenance it could have play in the timing around 120,000. miles hope this helped , please feel free to ask if you need any further assistance. Thank You.

Have you checked to make sure the convertors are not stopped up? you also could check for a vacuum leak around the intake manifold as well.