Enhance Engine Performance with MSD 5574 Street Fire Spark Plug Wire Set Review

These are spark plug cables. they do what they have to. I took off a star because the boot that goes around the spark plug is significantly smaller in diameter than the stock ones, making tightening a bit difficult in tight spaces.

It was amazing! I have noticed increased fuel consumption on my 99 Sierra 5.3L. Very easy to install. I'm only giving 4 stars because they don't hold the factory aluminum heat shield that comes on the factory plug wires so they have to be held while replugging the wires onto the plugs.

Installed by myself, drove it for a while, found my truck was misfiring. An ASE certified mechanic said they didn't match the factory setting and weren't making good contact with the spark plugs. I know it's definitely past the point of no going back, but a refund would still be nice considering the product was supposed to work effectively with my 2000 Chevy Silverado 5.3, but it doesn't. This explains the drop in performance I've noticed over the past few months.

They fit very well. I wish they snapped in a little tighter, but they should be fine. Also on the Silverado 04 if you reuse the heat shields they leave a pretty decent gap, the lugs that snap into the spark plug aren't as thick as the OEM wires causing the gap. Anyway, I still used the original heat shields, I think if that bothers you you could probably put some silicone between the heat shield and the wire to prevent any wobble.