I too went down the road of improving performance with a high comp head ram air injected by use of a megaphone inlet tube and megaphone exhaust, enlarged ports and inlet with a motor bike carby to fuel it along. Still never broke it.
With B&S buying Victa only to shut down 2 stroke production as not many buyers wanted a 4 stroke never mind a B&S piece of s**t. But GMH went and use Nissan motors in the Holden Commodore to get it to move along but had cooling issues with it, until they realised the problem and then resolved it.