Do NOT use a Home Depot plumbing coupler. You have a plastic upper intake manifold. When the torque of the motor rocks it in the mounts, the filter/heat shield hits the under side of the hood. The Home Depot coupler can't flex, which means the total force is transmitted to your plastic intake.
I don't have that problem for two reasons. I have a silcone flexible reducer like you're seeking, and I have a supercharger that can handle the stress, but let me give you an example of what I'm talking about, and imagine it with the hood closed:
Buy the 8224 coils from Jegs or Summit. I believe Jegs is the best price. Honestly, they're not going to gain you much power, and you MIGHT notice it in the mid range rpms, and a slightly smoother idle.