Re: timing ignition
Could be a valve train problem - but that sure is coincidental it picked the same time you changed ignition parts. What are the odds?
You've already localized it to #1. A module CANNOT affect only one cylinder, neither can a pick-up coil, or even the coil itself.
I can only be from the rotor outward, rotor, cap, wire, or plug, or the cylinder itself (see above.)
If you changed caps, you had to transfer the coil to the new cap - a possibility is you used the old style long screw - the long ones can crack the cap inside, letting the rotor jump the spark into the crack to the screw - which is ground. Look at the inside bottom of the cap.
Could be a bad wire or a bad plug. New doesn't mean good.
Pull the wire at the plug end - good healthy spark?
Yes - bad plug - sometimes when putting it in you miss the hole and get dirt on the nose of the plug, sometimes they are just bad new ones - put in an old one to try it.
No - pull the wire at the cap end - use a grounded wire to test for spark at the cap terminal.
Yes - bad wire.
No - look inside the cap for that crack.
Also look at the underside of the rotor - GM's are famous for flashing through the center of the rotor.
Please post the results here - most of the inconsiderate little kids on here don't bother to post the final results. That's how they've driven the adults away to other boards. Notice how few posts there are anymore - this board may get closed from inactivity.