TheL-Jetronic fuel injection has a temp sensor which allows the engine to run rich (and smoothly) until it warms up. Try
http://bama.ua.edu/bosch... or search L-Jetronic. There is a lot of stuff available.
My 924S has the original cat and it passed.
I know from experience that an engine that has sat for years needs a while to run in and get the friction down to where it should be. Can you get some miles on the car before you go for the inspection? An oil change might help too.
Dad cooked the engine, I love it. My son has done all the cookin in this family and I'm always doing the fixing.
Good luck,
Jon