99 civic ex b16y7
My long term fuel trim goes from 4.5 up to around 6 during highway driving.

I've done the following:

-bottle of Techron through the gas tank
-Fuel pressure is ~42PSI at idle with regulator hose pinched, 30 with regulator on at idle, 36 on highway under load.
-checked for vacuum leaks with carb cleaner
-checked 02 sensor output on an ultragauge; I know this isn't the best way to do it, but I did notice it hit both low and high numbers at about the same rate
-TPS output makes sense
-Coolant temp seems a bit low; it likes to hang around 163 during normal driving and will get up to 180 under load.
-MAP sensor output matches barometric pressure key on engine off
-I don't see or hear any leaks on the header

There is an evap leak somewhere, however I've clamped off the purge hose and nothing changes. Help would be hugely appreciated.