Years ago, extractors (combined with Holley & cam) was something that I put on most cars as soon as I bought them. Nowadays I wouldn't bother with extractors for a nice driver/cruiser unless it was necessary. Extractors scrape on speed bumps, hoists, driveways etc and seem over priced compared with what we used to pay, and don't seem to last either. Factory manifolds can have a good exhaust note if you run a twin system & experiment with a balance pipe. Its unusual to find a V8 Holden without them on the cars I look at. On the other hand extractors may improve your fuel economy if that's a consideration

cheers
Max