Just being Honda Centric, I think the high hp/displacement VTEC hondas have a difficult time. At already being 100 hp per liter, they don't have much to work with in terms of HP improvement. Del Sol VTEC is especially tough given its about 2350 dry and empty, about 150 pounds heavier than Civic Si with same engine. For picking winners, a trait that helps is finding a car with about 0.6 hp per liter. I think an engine at that power range best benefits with the mild compression, header, computer and intake improvements allowed in IT. If a car is at 100 hp/liter, its likely the manufacturer has already done those things.