Originally Posted by Modshack

I honestly don't think you're going to "notice" a difference. There has to be small improvements in flow though as smooth wall tube will obviously flow better than a corrugated one that would tend to disrupt smooth flow. Generally, a series of small improvements often add up to measurable gains, but just this one will not be a $100 kick in the pants. I've done both the Cobb and Generic 45 degree 2.75 elbows, but they've been in concert with my custom CAI mods...I didn't notice any change when I went from the stock hoses to the smooth walled silicone (both with my filters installed)

Generic hoses with custom PCV line take-offs on my car (before the Cobb's were available):


My friend Zpirate's car with the Cobb hoses: