It make me smile how some people would believe in god, and still not believe a dyno chart.
even if there's other mods on the engine, it prove one thing. these engine are highly restricted both ways. 10Whp is achievable with a simple ebay intake and a catback exhaust. let's say 50$ for the intake, 50$ for a large midpipe, and 50$ for a generic hi-flow muffler, and you're done. maybe i'm optimistic but it can be done for 200$ for sure.
then, think about what an hi-flow can and a headers can do.