imzjustplayin

I've noticed a decrease in fuel economy from a '96 Civic with a 1.6L non Vtec and a '98 Civic with a 1.6L non Vtec. I believe this decrease in fuel economy is due to tuning or de-tuning of the ECU as time has gone on. So my question is, if I take the ECU from a '96 civic 1.6L non vtec and put it into a '98, will this affect the smog check? I know you're not suppose to or allowed to put an older engine in a newer vehicle but would they be able to detect the difference in the ECUs? I don't believe there are any fundamental differences in the engines just in the ECU.