Misfire in 1998 Camaro

[hailey]

My cousin Darrell has a 1998 Camaro with a misfire and he just changed the spark plugs recently.Has the the LS1 and he installed the supposed to be good E3 spark plugs.My mechanic told him take them back getting the AC Delcos.Shows a PO300 code,My mechanic scanned it with his Tech 2 going to the misfire graphic,shows it on all cylinders.Finally told him it is the E3 spark plugs he installed.My cousin says it is not true.Ran good before changing the spark plugs and no check engine light on.I believe my mechanic,it is the spark plugs and my cousin is full of it.My mechanic fixed a missfire last week in a 1999 Camaro changing the spark plugs,someone else installed the E3 sparkplugs.

[Threlkeld's SS]

I had a 98 with e3 plugs and I didn't have any issues