Truck is running like total **** cel is flashing code p0300 multiple cylinder missfire is smell like gas at idle, I just did a tranny rebuild, and it has long tubes no cats and a single 3" dyno max just did plugs and wires on it as well

 

check for burnt wires first...

 

Yep where this dumbass header hump is @ cylinder 5 the wire is burnt

 

Mine was #7, I caught it with my Aeroforce guage. My SES light wasn't flashing yet, but I knew something wasn't right.

 

tis what I was gonna say, but looks like you found it. It took about a year for mine to burn thru using silicone socks. for my replacement wire on the #5 plug, I have put 2 of the foil type insulation sleeves over it & then the silicone sock. We'll see how long this one lasts

FWIW, anyone with Taylor wires, you can get individual wires from them, just have to call them & have them give you the part # & then order from Summit or Jegs(the taylor rep told me it would be cheaper to buy from someone else than directly from taylor)