1998 626 LX 2.0 L4 165,325 miles.
After starting, engine running rough and smoking out of exhaust. All 4 new spark plugs were sooted up. Trouble code was misfire #1 cylinder. Switched #1 & #2 plug wires and ran worse with trouble code misfire all cylinders. Switched back and ran better with misfire #1 again.

Recently replaced the timing belt, both bearings, spark plugs, water pump, and used coil pack from junk yard to fix back firing in the exhaust. Coil pack was the problem and not timing belt. Ran fine for 2 weeks.

Need help with my latest misfire issue,

 

Did not receive any replies to my request but did use the older "posts" to develop a plan to troubleshoot the repair.
Replaced the junk yard coil pack with a new "coil pack" and that fixed the misfire #1 cylinder. Also cleaned the throttle body and MAF sensor with the correct chemical sprays while I was at it. Mazda runs fine now!