Naturally Aspirated 2001 Corolla CE. 1.8L VVTi and no mods other than a drop-in K & N air-filter, semi-synthetic manual tranny fluid and synthetic engine oil. If I modded the exhaust, it would be a mild mod for smoother flow, not a huge increase in diameter etc. You're right about the increase in size possibly messing with flow and volumetric efficiency at lower RPM's. I'll do some research and plan a mild mod with possibly slightly increased diameter mandrel bent pipes as the main feature for improved flow. I actually wish I could make my car have better MPG on average, but also be able to go fast occasionally, but if that can't be done, I'll lean towards better fuel economy. For a grocery getter, the little Corolla goes fast enough when necessary, which, in reality, is almost never, especially when driving for fuel-economy. I'm glad I found this forum. I feel less crazy now when I see how many KM's I can coast with the engine off....lol...
