Had a friend that got his changed to local custom stainless steel type. But its' a 4:2:1 instead of stock 4:1. Complete with dummy cat and straight thru muffler, I can't catch up with his in straight runs especially the high revs.
To have a better effect, best is to mod the header(front end), the cat(mid end) and the muffler(rear end) all in one go. I reckon a 4:2:1 extractor actually boost the low end so low end torque is not affected too badly in this config? I heard reckless tampering of exhaust equipment might end up losing excessive low end torque. Gotta practise so caution is this area.