I used to have extractors (Hurricane) on my HG, but took them off for the standard manifolds.
Worked a treat with a standard 2 1/4" exhaust and 2 hot dogs, along with a nice note. (if i could transfer some footage from a video to CD i could show you).

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I had twin 2 1/4 dump pipes for the trip to Geelong, and couldn't wait to get home to remove them.
The drone inside for the 2 day trip (along with 3 kids), was just to much to handle.(was great around town though).