Okay, I’ll bite. For me, it’s those cheap, universal cold air intakes that just hang in the engine bay sucking up hot air. You see them all the time, and unless it’s a sealed system with a proper airbox or a well-designed ram-air setup, you’re often just paying for noise and maybe losing a bit of low-end torque. I’ve dyno’d cars where the stock box with a good panel filter made more consistent power. What’s the part you’ve seen people drop cash on that just doesn’t deliver?