The sound is better. It is a little deeper and can hear the SPS66 a little clearer. As far as spool up or power, dont no yet. I have not been able to find a clear, safe stretch of road to do a like for like launch that I know the numbers for. SOTP it does seem to be a little more responsive(spoolup?), but to many other mods already in place to know for sure. I will try to get some time this weekend to play and maybe even get to the track. I will post when I can be more specific. My EGTs have been so low since the SPS66 that I really dont pay a lot of attention to them. Of course that is a combo of air intake, turbo(MAINLY) and exhaust.