The question was asked, "WHy not just give the Lotus engines more turbo to make up the difference in horsepower between their engine and the Chevys and Hondas?"
Answer: "Too dangerous." My (admittedly poor) understanding is that the difference in base HP in the engines would require a turbo that would be like the "turbo boost" buttons on car video games - an giant boost of power that make the car hard to steer. There is a delay between mashing down the pedal and getting the turbo power as it is - I think too many HP would be in the "boost" (for lack of a better term) and would lead to spinning tires, etc. on the track.