first fix any and all cel. don't just go swapping plugs that look like they fit...run continuity tests from the ecu to the sensor-plugs directly. in the past week i've had half the cars come in w/ cel and half of those had pretty messed up plugs/wiring. just because it has a 2 or 3 wire plug and it reaches over doesn't mean it's the correct plug/sensor combination. plugging sensors in incorrectly can possibly burn out the sensor itself and/or ecu circuits.

second, you can't just drop any ecu in and it'll "pull hard"...even someone else's "tuned" ecu. you'll need to have it tuned to your setup.

at this point here's my suggestions:
1. fix cel
2. comp and leak down test
3. tune