Well depending on where you live, they might not be street legal. Here in Cali we need something called a CARB number on them. Those cost around 2-300. I had a pair of those nonbrand and they were great. I noticed smoother idling, great engine sound and they do give a little power too. So if in your state you don't need a certain number on them for smog purposes, id say get em. The 4-1 ones make your car loud as heck, and I would think you would have higher power from them...