check engine when i let off throttle

i figured out a while ago that my check engine light comes on when im driving and let off the throttle while still in gear, if i let off the throttle for more than say 3 seconds then the check engine light comes on. anybody knows what this is? im thinking it might be my wiring harness, because when i did my engine swap there are some cut and hanging plugs on my shock tower(think thats what its called), but i dont really feel any problems with my engine so i dont really mind, i am looking out for a new harness though because im sure those wires are there for a reason. also do you really feel a big difference with the check engine light on? i know it throws your car in safety mode or whatever, but i dont really feel any difference.

its a form of symbolizim telling you to go faster and keep ypur foot on the throttle

lol

I don't know much about cars too much. But if you say that you have mess around with the ECU, that means that the ECU is not reading the vacuum or something that involves while you let go of the throttle.

I don't know much about cars too much. But if you say that you have mess around with the ECU, that means that the ECU is not reading the vacuum or something that involves while you let go of the throttle.

I don't know much about cars too much. But if you say that you have mess around with the ECU, that means that the ECU is not reading the vacuum or something that involves while you let go of the throttle.

Whats with the three replys?

question,
i have a 95 gsr shell w/ 97 obd2 gsr engine. also an obd1 ecu. some of my wires/plugs are cut and hanging and i want to clean that up. do i need obd1 or obd2 wiring harness? thinking obd2? also i cant seem to find where to hook up the o2 sensor wire. the o2 sensor on my cat convertor, i follow the wire but it isnt even plugged in. cant find the plug where it goes, any help? only 1 o2 sensor?