Iridium plug gap

[GMC Rider]

I changed the plugs, wires, belts, and tensioners this weekend and everything went pretty smooth. I used iridium Delco plugs, and set the gap to .060 just like the owners manual said. The boxes the plugs came in also said "set gap to vehicle specs".

 

Today I came across a TSB that states the iridium plugs are factory set to .040 and should not be gapped due to possible damage to the plug. The truck runs great and it's not acting like I have any dead plugs, but should I expect shortened plug life or a fatal breakdown because I gapped them? Those little suckers are expensive!

 

2000 Sierra Z71 5.3L

Thanks

[GM-Tech]

I know of the TSB, but I can't say what specifically will happen if you gap them and use them. The TSB says if you get a new plug and it's not set to .040", don't use it. Sounds pretty serious, but I just don't have the details on what could happen.