You know you can check the cam timing without taking anything apart...
there is a little inspection hole next to the distributor, and a flat
groove mark on the side of the flywheel that will line up with a notch
in the bell housing (looking up from the bottom).  (there is also an
inspection window near the flywheel sensors behind the valve cover, but
that's harder to see.)  Because the cam spins once for every two
revolutions of the crank, the easiest way to do it is to put a 24mm
deep socket on the front crankshaft pulley nut, and turn it slowly
until you see the cam gear mark in the inspection hole (you'll probably
need a flashlight).  Once this mark is lined up, jack up the car, slide
under with your flash light (using all appropreate jack stands and
safety supports, of course) and look for the bottom flywheel mark.

If the cam timing is correct, I'd suggest a compression test next.  If
the compression test passes, then I'd think it's a spark or fuel
problem...  To diagnose that, take off ONE spark plug wire at a time
and try and start it up.  If you remove 1 wire, and the runs as poorly
as you've described, but no worse, then that's your screwed up
cylinder.

Good luck!  Let us know how you make out.

danger danger danger --- check your timing -
I bought a bunch of parts from a guy who had an "expert" work on his 924S -
the "expert" would put the timing belt on incorrectly and then when it would
slip tell him "oh, they all do that" and charge him for fixing it again -
and by incorrectly, I mean inside out.  I strongly suspect your belt was
incorrectly tensioned and skipped a tooth or three - Please, do yourself a
favor, READ THE BOOK and check the timing - a 7 year old can do it, you
certainly can too.