A local guy said that when he put bassani headers on his 03 Cobra he lost hp dyno proven I dont remember how much hp but it was like 20-30. Could this really happen and why?
1) Did he re-dyno at the same place/dyno as before? Different dynos can and will produce varying results. Add in temperature/barometic conditions, heat soak, etc, etc, and the engine could easily show a little variance in power on the dyno.
2) Were the headers the only change made before/after the dyno (ensuring it was not something else that contributed to the loss of power)?
3) Perhaps he lost a little peak hp/tq, but gained a significant amount of power under the area of the curve?