the .3 compression points are pretty low actually. The magic is in the cams, not much from the compression.
The headers combined with the headers will give you a big low end torque boost and the cams will take care of the top end. The combination is awesome. As long as you keep using a muffler, resonator and catalytic converter...even straight through designs, it will not be too loud. It will sound better, a bit more aggressive.
Former owner of '99 CSVT - Silver #222/2760
356/334 wHP/TQ at 10psi on pump gas!
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'05 Volvo S40 Turbo 5 AWD with 6spd, Passion Red
'06 Mazda5 Touring, 5spd,MTX, Black