in high horsepower engines, (engines that accelerate fast through the rpm range) told me that fast ecu mhz is needed. He said that stock ecus don't respond fast enough to changing conditions. Case in point is the 02 sensor looping 5 times in 10 seconds. He said that AEM is coming out with a unit for the Z soon. It is big bucks though. He told me that speed density has quicker response than MAF.