I bought a comp polymer upper (stock) and love it. Mid range increased slighly, under 2500 suffers a little but not that noticable on my light car.
I like the looks of it and it cleaned up my engine area giving me access to valve covers etc. I still have EGR, etc too.
Got mine on corral, used, $115.00.
You can modify a upper as you wanted, but its way too time consuming for very little gain.
__________________
Frank
|