I did the same install, turbo exhaust on a 2.4. My experience was exactly the same. I did some 0-60 runs using my G-Tech and measured no difference in power. Better look and (arguably) better sound are the only results.
Excelsior: Have you gotten a shipping quote for a one-piece exhaust, or are you guessing at the $100 ? By the way, cutting the pipe for shipping is a real questionable idea. I tried to reassemble one and it is no picnic.
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John
Lexington, KY
Sky VIN 00252
5-Sp Manual
Midnight Blue