Originally posted by 92lx
the header typically just does a small bit of polishing when it comes to the power curve. To be honest, basic bolt ons do not gain so much power than you can usually feel them big time. Usually a good intake is about the best gain. But the other two deffinately help the intake 
. Bolt ons together are only worth about 6-10hp in the end, depending on stock components.
- Nathan
I had a 6gen I-4 dynoed to tune someone's VAFC, and he gained 14.xx HP with I/H/E with a fan blowing into the engine.