[Shotimes] pcm problems on a 93 sho?

[Drnkslingr101@cs.com]

I took my 93 sho to the dealer because it was running rich(black carbon was 
coming from the exhaust when i  punched it) and it ocasionally didnt want to 
start but eventually would after numerous attempts,where the cylinders would 
freeze and stutter then finally fire and run. Though when this happens the 
tach does not work until I get it somewhere that I can step on it and can 
slam the the rpms up past 4000 then the tach springs to life and the check 
engine light goes off until the engine reaches running temp then the light 
comes back on. Also after 20 minutes or so of highway speeds the atx wants to 
slam into 2nd gear when I get into city stop and go driving unless I let off 
of the pedal just b-4 the anticipated shift. The dealer who allready got me 
for $750.00 says hes "confident" that it needs a pcm, thouhg after my last 
visit i am not so confident in theyre diagnosis since they offer no guarantee 
and no returning of computer parts.Also after they replaced the MAF,2 O2 
censors, and one other censor, my lite still comes on,they say its an egr 
code but checked my egr valve and found it to be ok.That is where they say it 
must be my pcm. Has anyone run into this before, the symptons are like 
clockwork and are a great way to ruin a nice drive.
p.s. If  when the engine wont turn over as above, if I wait it out usually 
about 5 to 10 minutes it will start and run fine except after reaching temp. 
the light will come back on but there seems to be no affect in performance.