[dstevens]

Our observation with the MAF based Honda ECUs is that any change to the intake system, and to a lessor degree the exhaust header, will alter the output of the MAF and generally screw things up. Even a small change well upstream of the MAF can cause turbulance and an incorrect signal. Most of the aftermarket has tried to match intake tube diameter only, without measuring the MAF output vs flow. We've found that switching to the regular MAP based system is better is most cases, which is an internal ECU 'operating system' change. Charlie's diagram has it bang on - especially the bottom left graph which shows the MAF output altered by the air intake.