I am running a stock ECU, OBDII, my kick is a 98' JX. The short term/long term fuel trim handles it with no issues.
I used a 4 degree offset timing key on the crank, this only advances the cam 2 degrees and the engine produces power down low that is smoothly available, no stumbles, no flatness, no detonation. Fuel mileage went up a fair amount over the stock cam and key.
I have a coated and wrapped XtremeZuks 16v header, 2.25" high flow Magnaflow cat, 2" mandrel bent exhaust piping, a turbo muffler with a K&N air filter for the stock airbox(gonna try a ricer conical filter sometime soon).