Well as of recently my truck as been kinda sluggish and it now makes a sound that kinda sounds like an exhaust leak when i accelerate and pops when i decelerate. I dont remember it popping as much as it does now but it does none the less. Im leaning towards clogged cat. so im probably going to have to either replace it with a high flow model or get an o2 simm and gut it. Im gonna do plugs this week and see how they look and then go from there. Btw any one know the autolite plug number for stock heat range and not 3923's?