I've had the Taylor shorties and new NGK plugs in my 03 for about 10,000 miles now. I also have it chipped to the 87 and the performance superchip tune. When i start the truck in the morning and let it idle it shakes a little bit which is definetely a misssing plug. It runs perfectly fine above idle but will do it again ramdomly when its idling at any time. I changed to premium with the performance tune and it went away for about a week but now does it occasionally again.

I have no codes or anything and i've pushed the boots on all of the plugs to make sure they are making contact.

Any thoughts on this?

 

only way to find a dead plug without taking them all out is putting it on a scope, if garages still do that.