what exactly is a whisper lid?how much horsepower does it add?

 

It is an aftermarket part to replace your stock airbox lid. All the restrictive elements have been removed and the surface is smooth so the air will move faster towards the TB.

As far as gains go, I'm sure there are dyno sheets about it, but I'd assume with a free-flowing filter it will add probably at least somewhere between 5-10 rwhp.

TS