Spark plugs

Yes, it could. Inspect those old plugs and either mark which cylinders they came out of or mark them just in case you do have questions later about which cylinders may be misfiring and why cause a look at the spark plugs could tell you why it misfires. Perhaps a plug is oil fouled and covered with motor oil, or maybe it is gas fouled and covered in gas or perhaps it is covered in carbon, crud, burnt, etc. A look at how the spark plug appears can give some clues as to what is going on in that particular cylinder.