Steve Campbell replied:

I have a 1HZ Troopie and previously had a 2F 60 Series. I put a 2.5 inch exhaust system in the 60 series with Genie extractors. Made a difference but wasn't huge. Plus more noise.

The difference in power between the 2H in the 60 series and the 1HZ is large enough that I'm not going to worry, but they do make a difference.

Peter Gordon replied:

Gary, a free flowing exhaust will only work as well as the rest of the engine allows, free flowing (clean)air filter, fuel pump settings etc. Extractors and larger diameter pipe will always improve performance to some extent. I found a website the advertises "super mufflers" supposed to increase fuel economy and performance. The site seems to say all the right things, but I will leave that decision up to you. If you go down this road let me know the results. The web address is www.nutech2000.com.au/prod10.htm. Hope this helps, Peter