[cobrashoch]

Generally fuel injection cleans up the hydocarbons side of the emitions mess and cat. converters get the bad exaust gas side of the emitions mess. Factory injection is usially a bit lean by performance standards (14.7 to 1) and this makes it better/easier for converters. High compression is bad on the gas side of emissions because higher compession brings higher pre combustion and higher resultant combustion temps, and this forms emissions with stronger chemical bonds that the converter cannot chemically break. So nope, your 2 valve engine can't be emitions complient without converters, esp. w/high compression. Modern 3 and 4 valve engines can change the hydocarbons side of emissions with manifold tuning and head runner tuning, and that's by in large why factorys are going this way. The added performance of these designs are really a side benifit, because the injection of even these performance engines is usially set a bit lean for true performance.
cobrashock