does it get worse as it warms up? I don't know anything about an L20et but thinking as if it were an L28et I'd also check the head temp sensor, clean the plugs on the ECU, put a long screw driver on each injector (while the motor is running) then put the screw driver next to your ear pressed against your head (temple area) to make sure they are all ticking. Take each plug out after running it and read them, are any of them wet? check the resistance of each plug wire. clean rotor surface under dizzy cap????