Hey guys this post is bout the '83 camaro in my sig. well, it has been stored for bout 6 months and i just got it out. put new gas in it and it stumbles really bad, backfires and just doesnt have any power. i played with the timing, not throwing any codes ixcept a 42. one thing i noticed while setting the timing, the timing mark jumps around quite a bit from like 0* to 8* but only simetimes.... the esc is disconnected.

 

Could be your distributor, I noticed that when I would try to set the timing on my car with the old 160,000 mile stocker in there it would jump around a bit. Then when i got my new MSD it was rock solid. Could be slop in the tolerances of your distributor or it could be the ignition module like Rob said. They're $33 at the local parts joint here in town.