Hot spark
 

I installed a set of MSD coils with new 8mm wires and NGK Iridium plugs today on my '14 Sierra 1500 and WOW!, after the first start up I noticed the difference, much quieter at idle and while driving it. I have an AirRaid intake tube to the stock air box and I used to really hear the throttle sound but no more, I thought I might have knocked something loose.. a little better on throttle response also!
I replaced the rear resonator/tail pipe with a 3" tail pipe, sounds much better and even with that it's still a quiet ride. :gmc2: