My 71 LT1, which is 100% original, runs poorly at speeds below 3500 RPM. Everyone I talk to say that it is normal for this car and that I should always try to keep the RPM's in the top 2/3 of the range. If anyone owns a 71 LT1 that doesn't run like stink below 3500 RPM, please respond. I actually hate driving mine due to this and am getting ready to give up if I can't correct the problem. It actually feels like it is missing. By the way, this car has been completely and professional restored from the ground up and is exactly as it was when original.