Changed plugs now rough idle
I have put these plugs in my car twice with no issues @ all.
To answer your question yes, you should check the gap before the install. They "should" be gapped @ .055!! Did you change your wires too? ,did you check your wires, to insure proper
fitment? Hope this helps. These are an Excellent plug for the LS1.
As far as the rough idle, I'd double check to ensure that all your wire boots are properly reconnected to the sparkplugs. #6 and #8 are always the most difficult IMO. If you have autotap you could also monitor misfires and see if anything unusual shows up on a particular cylinder.






