I think you may have solved the 'mystery'. Last night I was only measuring the pipes AFT of the Y split in the rear. Since there are two of them after the Y split, suppose that's not much restriction. I wasn't able to get under my car to measure upstream of the Y split. I am curious what our mid-pipe diameter is though, so SuperTony, if you don't mind measuring it for us, it would be a good data point. I know Deathshead believes the mid-pipe is the 2nd most restriction portion of our exhaust, short of the DP.