supercharger

if GM did produce an aftermarket engine mod it would be a turbo for the astra and secondly the engine without strengthening mods can't handle more than 3 psi of boost, and even then the clutch will need to be replaced often

I think I read someplace that the engine can hold more than 3 PSI, in fact most engines can hold more than that just because the manufacturers design and tune engines to be more fuel efficient for today's trends. I have heard rather good reviews on the 1.8L Ecotec Family 1 engine that is in this Vehicle. I do believe that a bolt on S/C will be available at some point, mostly because I want one as well just because I feel the low end power is rather poor. I wouldn't mind a turbo but that takes way more effort to install than a S/C Cheers :)

the 2008 saturn astra can support up to 10 psi without needing strengthening mods as you put it.